DOC: fixup spacing in to_csv docstring (GH22475)
Follow-up on https://github.com/pandas-dev/pandas/pull/22475
Hello @jorisvandenbossche! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/generic.py`](https://github.com/jorisvandenbossche/pandas/blob/4d84ba695349d035381543031142772e63604d3f/pandas/core/generic.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22816?src=pr&el=h1) Report
> Merging [#22816](https://codecov.io/gh/pandas-dev/pandas/pull/22816?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/64b88e86677349de66071dffd74b5c3254283e2a?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/22816/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22816?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22816   +/-   ##
=======================================
  Coverage   92.18%   92.18%           
=======================================
  Files         169      169           
  Lines       50820    50820           
=======================================
  Hits        46850    46850           
  Misses       3970     3970
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `42.38% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22816?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/22816/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.67% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22816?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/22816?src=pr&el=footer). Last update [64b88e8...4d84ba6](https://codecov.io/gh/pandas-dev/pandas/pull/22816?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
