[jdk20] RFR: 8298525: javadoc crashes with "UnsupportedOperationException: Not yet implemented" in SeeTaglet.inherit

[Pavel Rappo]

This makes JavaDoc warn, not crash, if `{@inheritDoc}` appears in the `@see` tag and the newer `@spec` tag. This is a jurry-rigged patch to fix an infrequent and erroneous case that should be properly revisited later.

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk20/pull/84/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20&pr=84&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298525
  Stats: 27 lines in 3 files changed: 21 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk20/pull/84.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/84/head:pull/84

PR: https://git.openjdk.org/jdk20/pull/84