Strict fields JEP is now assigned number [539](https://openjdk.org/jeps/539). Update the references in the documentations.
--------- - [x] I confirm that I make this contribution in accordance with the [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). ------------- Commit messages: - Strict fields is JEP 539 Changes: https://git.openjdk.org/valhalla/pull/2596/files Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2596&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8387454 Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod Patch: https://git.openjdk.org/valhalla/pull/2596.diff Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2596/head:pull/2596 PR: https://git.openjdk.org/valhalla/pull/2596
