RFR: 8346128: Comparison build fails due to difference in LabelTarget.html

[Nizar Benalla]

Please review this doc-only patch to fix an issue that causes the cmp-baseline build to fail.

The snippet in `LabelTrget.java` showed a highly rare non deterministism in javadoc snippet generation, which will be fixed in [JDK-8346659](https://bugs.openjdk.org/browse/JDK-8346659), but we can fix the snippet now to stop the failures.

Previously, "label" in "labelBinding" would be matched to either `CodeBuilder#labelBinding` or `LabelTarget#label` (about 50:50 chance of either happening). I repaced the substring with a regex which seems to fix the issue.

This will need to be backported to JDK 24.

TIA!

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Commit messages:
 - use regex instead of substring to match for label() method

Changes: https://git.openjdk.org/jdk/pull/22834/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22834&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346128
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22834.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22834/head:pull/22834

PR: https://git.openjdk.org/jdk/pull/22834