RFR: 8336040: Missing closing anchor element in Docs.gmk

[Nizar Benalla]

Can I please have a review for this bug fix to make file used to generate the OpenJDK documentation. It adds the missing `</a>` tag after `OTHER SPECIFICATIONS`, this should help remove some HTML warnings in out generated docs.

Thanks in advance.

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

Commit messages:
 - (C)
 - Added closing hyperlink tag after OTHER SPECIFICATIONS

Changes: https://git.openjdk.org/jdk/pull/20195/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20195&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336040
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/20195.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20195/head:pull/20195

PR: https://git.openjdk.org/jdk/pull/20195