DOC: Added series example variable to flex_doc

[James-Gilbert-]

-closes #23069

[pep8speaks]

Hello @James-Gilbert-! Thanks for submitting the PR.

• There are no PEP8 issues in the file pandas/core/ops.py !

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@e4b67ca). Click here to learn what that means.
The diff coverage is 100%.

@@            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	Coverage Δ
pandas/core/ops.py	97.19% <100%> (ø)

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[codecov]

Codecov Report

Merging #23117 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            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)	⬆️
#single	42.25% <100%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/ops.py	97.19% <100%> (ø)	⬆️

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[datapythonista]

I think this conflicts with #20415 which will be merged soon.

[WillAyd]

Closing this due to conflict with other PR