RFR: JDK-8309134: Augment test/langtools/tools/javac/versions/Versions.java for JDK 21 language changes

[Joe Darcy]

Augment the Versions.java test in the usual way for new language changes.

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Commit messages:
 - JDK-8309134: Augment test/langtools/tools/javac/versions/Versions.java for JDK 21 language changes

Changes: https://git.openjdk.org/jdk/pull/14229/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14229&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309134
  Stats: 30 lines in 1 file changed: 25 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/14229.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14229/head:pull/14229

PR: https://git.openjdk.org/jdk/pull/14229