RFR: 8340399: Update comment in SourceVersion for language evolution history

[Joe Darcy]

Update comment in include recent language evolution.

-------------

Commit messages:
 - JDK-8340399: Update comment in SourceVersion for language evolution history

Changes: https://git.openjdk.org/jdk/pull/21068/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21068&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340399
  Stats: 8 lines in 1 file changed: 6 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21068.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21068/head:pull/21068

PR: https://git.openjdk.org/jdk/pull/21068