[jdk21] RFR: 8312098: Update man page for javadoc

[Jim Laskey]

Update javadoc man page to indicate unnamed classes are supported.

-------------

Commit messages:
 - 8312098: Update man page for javadoc (closed)

Changes: https://git.openjdk.org/jdk21/pull/130/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21&pr=130&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312098
  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk21/pull/130.diff
  Fetch: git fetch https://git.openjdk.org/jdk21.git pull/130/head:pull/130

PR: https://git.openjdk.org/jdk21/pull/130