RFR: 8361303: L10n comment for javac.opt.Xlint.desc.synchronization in javac.properties

[Justin Lu]

Please review this PR which provides a comment to make apparent what should not be localized in the value for the key: `javac.opt.Xlint.desc.synchronization`. This was suggested by the translation team and is also consistent with other key values in the properties file that make similar comments.

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Commit messages:
 - init

Changes: https://git.openjdk.org/jdk/pull/26105/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26105&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361303
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26105.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26105/head:pull/26105

PR: https://git.openjdk.org/jdk/pull/26105