RFR: 8277944: JDK 18 - update GA Release Date

[Pavel Kharskii]

8277944: JDK 18 - update GA Release Date

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

Commit messages:
 - 8277944: JDK 18 - update GA Release Date

Changes: https://git.openjdk.java.net/jdk/pull/6596/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6596&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277944
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6596.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6596/head:pull/6596

PR: https://git.openjdk.java.net/jdk/pull/6596