[jdk20] RFR: JDK-8299147: Minor accessibility errors in the specs and man index pages

[Jonathan Gibbons]

Please review a trivial accessibility fix for the "draft" header in a couple of index file.

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Commit messages:
 - JDK-8299147: Minor accessibility errors in the specs and man index pages

Changes: https://git.openjdk.org/jdk20/pull/66/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20&pr=66&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299147
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk20/pull/66.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/66/head:pull/66

PR: https://git.openjdk.org/jdk20/pull/66