Citus 11.3 documentation update checklist

[pinodeca]

• [x] Ensure git cherry-picks up to date on master branch
• [x] Bump version
  • :vimgrep '\(\<11\.\?2\>\)\|\(112_\)' **/*.rst *.py
• [x] Update installation (need input from #1079)
• [x] Update our upgrade steps (need input from #1079)
• [x] Update citusdata.com/download links.
• [ ] scan for any other udf and guc changes (in Community and Enterprise)
  • git diff origin/release-11.2 origin/release-11.3 -- src/backend/distributed/shared_library_init.c
  • git diff origin/release-11.2 origin/release-11.3 -- src/backend/distributed/sql/udfs/
  • Also check https://github.com/citusdata/citus/pull/6856
• [x] Verify there are no Sphinx warnings in local build
  • sphinx-build -b html -a -n -W . _build
  • (Remove _build directory and try fresh too)
• [x] Create new 11.3 release branch
• [x] Test that the search box works in the new release branch
• [x] Set as default ver in RTD (advanced settings tab)
• [x] Rebuild previous version so that canonical link gets updated
• [ ] Re-check old versions (does the version picker work, does search work)