Fix minor typo
Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25458?src=pr&el=h1) Report
> Merging [#25458](https://codecov.io/gh/pandas-dev/pandas/pull/25458?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/aa084162bcaa7ce0efdc044bc8077f6bfca70674?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25458/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25458?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25458      +/-   ##
==========================================
+ Coverage   91.74%   91.74%   +<.01%     
==========================================
  Files         173      173              
  Lines       52923    52923              
==========================================
+ Hits        48554    48555       +1     
+ Misses       4369     4368       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.31% <ø> (ø)` | :arrow_up: |
| #single | `41.73% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25458?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/25458/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `94.16% <ø> (ø)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25458/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.66% <0%> (+0.09%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25458?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/25458?src=pr&el=footer). Last update [aa08416...e60b0b1](https://codecov.io/gh/pandas-dev/pandas/pull/25458?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/25458?src=pr&el=h1) Report
> Merging [#25458](https://codecov.io/gh/pandas-dev/pandas/pull/25458?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/c9863865c217867583e8f6592ba88d9200601992?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/25458/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25458?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25458      +/-   ##
==========================================
- Coverage   91.74%   91.74%   -0.01%     
==========================================
  Files         173      173              
  Lines       52923    52923              
==========================================
- Hits        48555    48554       -1     
- Misses       4368     4369       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.31% <ø> (ø)` | :arrow_up: |
| #single | `41.73% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25458?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/25458/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `94.16% <ø> (ø)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25458/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.57% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25458?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/25458?src=pr&el=footer). Last update [c986386...eca7f6f](https://codecov.io/gh/pandas-dev/pandas/pull/25458?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Failures appear to be a result of an isort change so unrelated, but might see if we can fix that first and ask you to rebase thereafter just to be safe PR for issue above is #25455 Can you merge master? Just had a PR go in that should resolve build failures thanks @pombredanne 