RFR: 8332099: Add `@since` to package-info in `jdk.jsobject`

[Nizar Benalla]

Simple code cleanup.
If you're reviewing this, thanks.

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Commit messages:
 - (C)
 - Add `@since` to package-info.java in `jdk.jsobject`

Changes: https://git.openjdk.org/jdk/pull/19197/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19197&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332099
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19197.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19197/head:pull/19197

PR: https://git.openjdk.org/jdk/pull/19197