DOC: Added series example variable to flex_doc
-closes #23069
Hello @James-Gilbert-! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/ops.py`](https://github.com/James-Gilbert-/pandas/blob/93e8cf5eb973347bbac0c951e5d2111f70e57b5b/pandas/core/ops.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23117?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@e4b67ca`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23117/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23117?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #23117   +/-   ##
=========================================
  Coverage          ?    92.2%           
=========================================
  Files             ?      169           
  Lines             ?    50889           
  Branches          ?        0           
=========================================
  Hits              ?    46920           
  Misses            ?     3969           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.62% <100%> (?)` | |
| #single | `42.24% <100%> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23117?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/23117/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvb3BzLnB5) | `97.19% <100%> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23117?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/23117?src=pr&el=footer). Last update [e4b67ca...e38c019](https://codecov.io/gh/pandas-dev/pandas/pull/23117?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/23117?src=pr&el=h1) Report
> Merging [#23117](https://codecov.io/gh/pandas-dev/pandas/pull/23117?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e4b67ca725db373afe8f4565672eb16e1e8e3b31?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23117/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23117?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23117      +/-   ##
==========================================
+ Coverage   92.21%   92.21%   +<.01%     
==========================================
  Files         169      169              
  Lines       50884    50885       +1     
==========================================
+ Hits        46922    46923       +1     
  Misses       3962     3962
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.63% <100%> (ø)` | :arrow_up: |
| #single | `42.25% <100%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23117?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/23117/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvb3BzLnB5) | `97.19% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23117?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/23117?src=pr&el=footer). Last update [e4b67ca...e38c019](https://codecov.io/gh/pandas-dev/pandas/pull/23117?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 I think this conflicts with #20415 which will be merged soon. Closing this due to conflict with other PR