Fix a small typo
- [x] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

This PR fixes a small typo : Alternativly -> Alternatively.
Thanks for the awesome project!
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=h1) Report
> Merging [#17811](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e63c935d5a0705f83fc726932eb82bac4c272106?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/17811/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17811      +/-   ##
==========================================
- Coverage   91.26%   91.24%   -0.02%     
==========================================
  Files         163      163              
  Lines       49978    49978              
==========================================
- Hits        45611    45602       -9     
- Misses       4367     4376       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.04% <ø> (ø)` | :arrow_up: |
| #single | `40.24% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/reshape.py](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9yZXNoYXBlLnB5) | `99.27% <ø> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.74% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17811?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/17811?src=pr&el=footer). Last update [e63c935...69650ac](https://codecov.io/gh/pandas-dev/pandas/pull/17811?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/17811?src=pr&el=h1) Report
> Merging [#17811](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e63c935d5a0705f83fc726932eb82bac4c272106?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/17811/graphs/tree.svg?token=eZ4WkYLtcO&width=650&src=pr&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17811      +/-   ##
==========================================
- Coverage   91.26%   91.24%   -0.02%     
==========================================
  Files         163      163              
  Lines       49978    49978              
==========================================
- Hits        45611    45602       -9     
- Misses       4367     4376       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.04% <ø> (ø)` | :arrow_up: |
| #single | `40.24% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/reshape.py](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9yZXNoYXBlLnB5) | `99.27% <ø> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.74% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17811?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/17811?src=pr&el=footer). Last update [e63c935...69650ac](https://codecov.io/gh/pandas-dev/pandas/pull/17811?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thank you!