chore: fix generate-release-docs.sh for per-Spark-version doc layout

[mbutrovich]

Which issue does this PR close?

Closes #.

Rationale for this change

dev/generate-release-docs.sh freezes generated docs onto a release branch. It has been broken since #4139, which split compatibility/expressions/ into per-Spark-version subdirectories (spark-3.4 .. spark-4.1) plus _category_template/. That PR updated the publish-time generator (docs/build.sh) and GenerateDocs but not this script, so it still called GenerateDocs with only the user-guide root, hit the removed flat path, and failed with FileNotFoundException: .../compatibility/expressions/cast.md. No release has been cut since, so it went unnoticed.

What changes are included in this PR?

Bring the script in line with docs/build.sh: loop the Spark profiles, copy _category_template/*.md into each spark-<ver>/, and run GenerateDocs per profile with -Dexec.arguments="<latest-user-guide>,<profile>" to pass the subdirectory arg. Also run prettier --write over the output, since CI checks prettier --check "**/*.md" and this script (unlike build.sh, whose temp output is throwaway) commits its result. _category_template/ is kept as committed source. The only difference from build.sh is that this runs against the source tree so the freeze can be committed. The same fix lands on branch-0.17 bundled with the generated docs freeze; on main the generated docs are not committed, so this PR carries the script change alone.

How are these changes tested?

Ran on a 0.17.0 release branch: configs.md populated, all four spark-<ver>/ dirs contain cast.md plus category pages with filled tables, per-version differences land where expected (map.md/misc.md differ 3.4 vs 4.1, misc.md differs 3.4 vs 3.5, 4.0 == 4.1), and prettier --check passes.

[andygrove]

Thanks for fixing this @mbutrovich!