RFR: 8312106: Update man page for javadoc

[Jim Laskey]

Update javadoc man page to indicate unnamed classes are supported.

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Commit messages:
 - 8312106: Update man page for javadoc

Changes: https://git.openjdk.org/jdk/pull/14891/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14891&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312106
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/14891.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14891/head:pull/14891

PR: https://git.openjdk.org/jdk/pull/14891