Incorrect example in wide_to_long docstring

[sanjusci]

• closes Incorrect example in wide_to_long docstring #25733
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[codecov]

Codecov Report

Merging #26010 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #26010      +/-   ##
==========================================
- Coverage   91.82%   91.81%   -0.01%     
==========================================
  Files         175      175              
  Lines       52551    52551              
==========================================
- Hits        48256    48252       -4     
- Misses       4295     4299       +4

Flag	Coverage Δ
#multiple	90.38% <ø> (ø)	⬆️
#single	40.72% <ø> (-0.14%)	⬇️

Impacted Files	Coverage Δ
pandas/core/reshape/melt.py	97.5% <ø> (ø)	⬆️
pandas/io/gbq.py	75% <0%> (-12.5%)	⬇️
pandas/core/frame.py	96.79% <0%> (-0.12%)	⬇️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #26010 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #26010      +/-   ##
==========================================
- Coverage   91.82%   91.81%   -0.01%     
==========================================
  Files         175      175              
  Lines       52551    52551              
==========================================
- Hits        48256    48252       -4     
- Misses       4295     4299       +4

Flag	Coverage Δ
#multiple	90.38% <ø> (ø)	⬆️
#single	40.72% <ø> (-0.14%)	⬇️

Impacted Files	Coverage Δ
pandas/core/reshape/melt.py	97.5% <ø> (ø)	⬆️
pandas/io/gbq.py	75% <0%> (-12.5%)	⬇️
pandas/core/frame.py	96.79% <0%> (-0.12%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a1fee91...5d160ab. Read the comment docs.

[WillAyd]

There are a few more things in the original PR that we would want to include here, namely adding this module to the CI checks. Can you do that here as well?

[WillAyd]

Can you check CI failures? Related to change

[WillAyd]

superseded by #26273