DOC: Fix missing parentheses in documentation
Add parentheses to fix `SyntaxError: Missing parentheses in call to 'print'` inside documentations. 

 - [ ] closes #xxxx
 - [ ] tests added / passed
 - [ ] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff`` (On Windows, ``git diff upstream/master -u -- "*.py" | flake8 --diff`` might work as an alternative.)
 - [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=h1) Report
> Merging [#16862](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9c44f9b2cad863bde17c7dd061d5b5b5ccbada21?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16862/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16862      +/-   ##
==========================================
- Coverage   90.98%   90.96%   -0.03%     
==========================================
  Files         161      161              
  Lines       49300    49300              
==========================================
- Hits        44857    44847      -10     
- Misses       4443     4453      +10
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.74% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.18% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.71% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.23% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16862?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/16862?src=pr&el=footer). Last update [9c44f9b...006d50c](https://codecov.io/gh/pandas-dev/pandas/pull/16862?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/16862?src=pr&el=h1) Report
> Merging [#16862](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9c44f9b2cad863bde17c7dd061d5b5b5ccbada21?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16862/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16862      +/-   ##
==========================================
- Coverage   90.98%   90.96%   -0.03%     
==========================================
  Files         161      161              
  Lines       49300    49300              
==========================================
- Hits        44857    44847      -10     
- Misses       4443     4453      +10
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.74% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.18% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.71% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.23% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16862?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/16862?src=pr&el=footer). Last update [9c44f9b...006d50c](https://codecov.io/gh/pandas-dev/pandas/pull/16862?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!