RFR: 8334162: Gatherer.defaultCombiner has an erronous @see-link

[Viktor Klang]

Erronous Javadoc reference addressed. This should be backported to 23.

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Commit messages:
 - Updating Gatherer#defaultCombiner Javadoc to refer to Gatherer#combiner

Changes: https://git.openjdk.org/jdk/pull/19682/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19682&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334162
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19682.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19682/head:pull/19682

PR: https://git.openjdk.org/jdk/pull/19682