[SPARK-60234][INFRA] During releases create a single spark-website commit

[nchammas]

What changes were proposed in this pull request?

During a release, create only one spark-website commit and push.

In other words, instead of having both:

• "Add docs for Apache Spark 3.5.9" apache/spark-website@136c848
• "Add release docs for Apache Spark 3.5.9" apache/spark-website@7d894fa

We'd have a single spark-website commit: "Update docs and website for Apache Spark 3.5.9"

Why are the changes needed?

There is no need for two separate commits. They appear to be a historical artifact rather than a conscious design choice.

The separate commits also make it more likely that someone will later inadvertently re-introduce the double push that we eliminated in #59071, which may trigger some annoying push failures due to the new spark-website CI setup.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Tested locally via GitHub Copilot with a disposable Git repository and bare remote. The exact git add . → git commit → git push origin HEAD:asf-site flow successfully included documentation.md, generated docs, and nested assets in one commit. Also passed bash -n and git diff --check.

Was this patch authored or co-authored using generative AI tooling?

I wrote this with assistance from Github Copilot.

[cloud-fan]

@HyukjinKwon the release GA job always use the scripts from the master branch? then this PR can be master only

[nchammas]

I'll merge this in to master only for now, but yes, I would like to confirm whether we need to also backport this PR as well as #59071 to all active branches so that the release process works as intended.

[uros-b]

LGTM, script change itself is good but I would backport as @nchammas sugggested

Process note: .github/workflows/release.yml checks out the release branch and only overlays dev/create-release/spark-rm/Dockerfile.base from master. A 4.x finalize will keep the old two-commit website path unless this is backported to branch-4.x (and e.g. branches like branch-4.3 if those still cut releases in the future).