DOC: Removing keep=False from docs on nlargest/nsmallest
- [x] closes #18559 
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18617?src=pr&el=h1) Report
> Merging [#18617](https://codecov.io/gh/pandas-dev/pandas/pull/18617?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/6e56195fcb021e7c53301722804087ef2a83bc39?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/18617/graphs/tree.svg?height=150&width=650&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/18617?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18617      +/-   ##
==========================================
- Coverage   91.46%   91.45%   -0.02%     
==========================================
  Files         157      157              
  Lines       51449    51449              
==========================================
- Hits        47060    47051       -9     
- Misses       4389     4398       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.32% <ø> (ø)` | :arrow_up: |
| #single | `40.6% <ø> (-0.11%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18617?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/18617/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `94.8% <ø> (ø)` | :arrow_up: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18617/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.81% <ø> (-0.1%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18617/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18617?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/18617?src=pr&el=footer). Last update [6e56195...c8ca144](https://codecov.io/gh/pandas-dev/pandas/pull/18617?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/18617?src=pr&el=h1) Report
> Merging [#18617](https://codecov.io/gh/pandas-dev/pandas/pull/18617?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/6e56195fcb021e7c53301722804087ef2a83bc39?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/18617/graphs/tree.svg?height=150&width=650&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/18617?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18617      +/-   ##
==========================================
- Coverage   91.46%   91.45%   -0.02%     
==========================================
  Files         157      157              
  Lines       51449    51449              
==========================================
- Hits        47060    47051       -9     
- Misses       4389     4398       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.32% <ø> (ø)` | :arrow_up: |
| #single | `40.6% <ø> (-0.11%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18617?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/18617/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `94.8% <ø> (ø)` | :arrow_up: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18617/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.81% <ø> (-0.1%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18617/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18617?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/18617?src=pr&el=footer). Last update [6e56195...c8ca144](https://codecov.io/gh/pandas-dev/pandas/pull/18617?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!