DOC: Fix outdated default values in util.testing docstrings
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @dargueta! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/util/testing.py`](https://github.com/dargueta/pandas/blob/03d98e9414b869f1c6b302154864c347e7124e80/pandas/util/testing.py) !

 - Complete extra results for this file :

> file_to_check.py:2407:-258: W605 invalid escape sequence '\('
file_to_check.py:2407:-255: W605 invalid escape sequence '\)'
---

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22776?src=pr&el=h1) Report
> Merging [#22776](https://codecov.io/gh/pandas-dev/pandas/pull/22776?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1c113db60b68c5a262d64e92dc9de72bfe59aed5?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/22776/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22776?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22776   +/-   ##
=======================================
  Coverage   92.17%   92.17%           
=======================================
  Files         169      169           
  Lines       50778    50778           
=======================================
  Hits        46807    46807           
  Misses       3971     3971
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.59% <ø> (ø)` | :arrow_up: |
| #single | `42.33% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22776?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/22776/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `86.03% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22776?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/22776?src=pr&el=footer). Last update [1c113db...4fed465](https://codecov.io/gh/pandas-dev/pandas/pull/22776?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @dargueta Thanks !