RFR: 8279115: Fix internal doc comment errors.

[Jonathan Gibbons]

Please review a trivial fix to some internal comments, to remove some irritating errors when running javadoc on its own internal classes.

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Commit messages:
 - 8279115: Fix internal doc comment errors.

Changes: https://git.openjdk.java.net/jdk/pull/6913/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6913&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279115
  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6913.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6913/head:pull/6913

PR: https://git.openjdk.java.net/jdk/pull/6913