Fix Java25ProjectTestSetup for Java 26

[stephan-herrmann]

• preview is no longer a valid option for release 25

Fixes regressions in JavadocQuickFixTest25

[stephan-herrmann]

Build failure is the same as reported in #2740 (comment) - apparently eclipse-jdt/eclipse.jdt.core#4664 has not yet appeared in https://download.eclipse.org/eclipse/updates/4.39-Y-builds. The latest Y-build should actually have the fix, but I guess the comparator errors prevent that Y-build from being listed in the composite of 4.39-Y-builds. I will wait one successful Y-build after eclipse-jdt/eclipse.jdt.core#4778 to see if that resolved both the comparator error, and in the sequel also the build of this PR.

[stephan-herrmann]

closing because this jobs .m2/ has an invalid entry /home/jenkins/agent/workspace/eclipse.jdt.ui-github_PR-2752/.m2/repository/p2/osgi/bundle/org.eclipse.jdt.core/3.45.50.v20251129-2047/org.eclipse.jdt.core-3.45.50.v20251129-2047.jar (until recently jdt.core had an extra, unneeded version increment in the branch).

[stephan-herrmann]

trying again at #2754