CI: Unpin Miniconda for CI
Closes https://github.com/pandas-dev/pandas/issues/17696

xref https://github.com/pandas-dev/pandas/pull/17700
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=h1) Report
> Merging [#17752](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/2ff1241fa794231b8317ebe96b66f71dce99e0c2?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17752/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17752      +/-   ##
==========================================
- Coverage   91.23%   91.23%   -0.01%     
==========================================
  Files         163      163              
  Lines       49869    49856      -13     
==========================================
- Hits        45499    45487      -12     
+ Misses       4370     4369       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.03% <ø> (+0.01%)` | :arrow_up: |
| #single | `40.25% <ø> (-0.06%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.34% <0%> (-0.12%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.73% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.48% <0%> (-0.1%)` | :arrow_down: |
| [pandas/io/formats/excel.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZXhjZWwucHk=) | `96.65% <0%> (-0.05%)` | :arrow_down: |
| [pandas/core/indexing.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhpbmcucHk=) | `93.94% <0%> (-0.04%)` | :arrow_down: |
| [pandas/core/internals.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzLnB5) | `94.37% <0%> (-0.01%)` | :arrow_down: |
| [pandas/plotting/\_style.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19zdHlsZS5weQ==) | `74.28% <0%> (ø)` | :arrow_up: |
| [pandas/io/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2lvL2h0bWwucHk=) | `85.17% <0%> (+0.31%)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.2% <0%> (+1.81%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=footer). Last update [2ff1241...5d7e853](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=h1) Report
> Merging [#17752](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/2ff1241fa794231b8317ebe96b66f71dce99e0c2?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17752/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17752      +/-   ##
==========================================
- Coverage   91.23%   91.22%   -0.02%     
==========================================
  Files         163      163              
  Lines       49869    49869              
==========================================
- Hits        45499    45491       -8     
- Misses       4370     4378       +8
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.02% <ø> (ø)` | :arrow_up: |
| #single | `40.24% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.73% <0%> (-0.1%)` | :arrow_down: |
| [pandas/io/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=tree#diff-cGFuZGFzL2lvL2h0bWwucHk=) | `85.17% <0%> (+0.31%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=footer). Last update [2ff1241...5d7e853](https://codecov.io/gh/pandas-dev/pandas/pull/17752?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 lgtm.  I may wait to see what's going on in https://github.com/conda-forge/pytables-feedstock/issues/19 before merging this. @TomAugspurger yeah I think that the recipe for that is messed up. they claim its a zlbi thing, but not so sure. I think this is fine (and the pytables issue is now fixed). merging. Great, thanks.

On Thu, Oct 5, 2017 at 1:37 PM, Jeff Reback <notifications@github.com>
wrote:

> Merged #17752 <https://github.com/pandas-dev/pandas/pull/17752>.
>
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