RFR: CODETOOLS-7903171: Fix issues related to generating internal API documentation

[Jonathan Gibbons]

Please review some trivial changes to update the makefiles and doc comments used to generate internal API documentation

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Commit messages:
 - CODETOOLS-7903171: Fix issues related to generating internal API documentation

Changes: https://git.openjdk.java.net/jtreg/pull/79/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtreg&pr=79&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903171
  Stats: 23 lines in 5 files changed: 1 ins; 1 del; 21 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/79.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/79/head:pull/79

PR: https://git.openjdk.java.net/jtreg/pull/79