RFR: 8374538: Wrong specification of MethodHandles.constant(...)

[Hannes Greule]

A simple correction to the javadocs of `MethodHandles.constant(...)`. Please review and let me know what you think.

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Commit messages:
 - adjust javadoc

Changes: https://git.openjdk.org/jdk/pull/29174/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29174&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374538
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/29174.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29174/head:pull/29174

PR: https://git.openjdk.org/jdk/pull/29174