DOC: some editing of 0.20 whatsnew file
- moved pandas.errors and pandas.testing to the reorganization section
- put ix and panel deprecations under deprecations
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=h1) Report
> Merging [#16085](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1f16ca7a821b705010197c37b529f494060888c3?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/16085/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16085      +/-   ##
==========================================
- Coverage   90.84%   90.84%   -0.01%     
==========================================
  Files         159      159              
  Lines       50790    50774      -16     
==========================================
- Hits        46142    46126      -16     
  Misses       4648     4648
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.62% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.35% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.54% <0%> (-1.82%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `79.38% <0%> (-0.25%)` | :arrow_down: |
| [pandas/util/importing.py](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvaW1wb3J0aW5nLnB5) | | |
| [pandas/tools/hashing.py](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree#diff-cGFuZGFzL3Rvb2xzL2hhc2hpbmcucHk=) | | |
| [pandas/formats/style.py](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree#diff-cGFuZGFzL2Zvcm1hdHMvc3R5bGUucHk=) | `100% <0%> (ø)` | |
| [pandas/util/hashing.py](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvaGFzaGluZy5weQ==) | `99.02% <0%> (ø)` | |
| [pandas/io/api.py](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=tree#diff-cGFuZGFzL2lvL2FwaS5weQ==) | `100% <0%> (+28.57%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16085?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/16085?src=pr&el=footer). Last update [1f16ca7...860c08a](https://codecov.io/gh/pandas-dev/pandas/pull/16085?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
