DOC: Not pushing the docs to github pages in PRs

[datapythonista]

In #24292 we made the doc build fail when there is a failure. But in PR builds, pushing to github pages is expected to fail, so the build job is failing for every PR now. Pushing docs to github pages only for master builds in this PR (we still build the docs, to make sure it doesn't fail).

[codecov]

Codecov Report

Merging #24316 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #24316   +/-   ##
=======================================
  Coverage   92.28%   92.28%           
=======================================
  Files         162      162           
  Lines       51831    51831           
=======================================
  Hits        47831    47831           
  Misses       4000     4000

Flag	Coverage Δ
#multiple	90.68% <ø> (ø)	⬆️
#single	43.01% <ø> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #24316 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #24316   +/-   ##
=======================================
  Coverage   92.28%   92.28%           
=======================================
  Files         162      162           
  Lines       51831    51831           
=======================================
  Hits        47831    47831           
  Misses       4000     4000

Flag	Coverage Δ
#multiple	90.68% <ø> (ø)	⬆️
#single	43.01% <ø> (ø)	⬆️

---

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 41780e5...75f1434. Read the comment docs.

[jreback]

thanks