Oracle no longer serves JDK 21 under /java/21/latest/, so a major-only
request falls back to the archived 21 GA build and reports version 21.
The e2e check required a concrete version for floating Oracle requests,
so the oracle 21 jobs failed.
Move floating Oracle e2e coverage to JDK 25 and keep a single oracle 21
job that exercises the archive fallback without the concrete-version
requirement. Warn when a major-only request falls back from /latest/ to
the archived GA release, since that build may lack security updates.
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>