RFR: 8356108: Update SourceVersion.RELEASE_25 description for JEPs 511 and 512

[Joe Darcy]

Expected update to keep the description of language evolution accurate.

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Commit messages:
 - JDK-8356108: Update SourceVersion.RELEASE_25 description for JEPs 511 and 512

Changes: https://git.openjdk.org/jdk/pull/25015/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25015&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356108
  Stats: 19 lines in 2 files changed: 17 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/25015.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25015/head:pull/25015

PR: https://git.openjdk.org/jdk/pull/25015