RFR: 8351897: Extra closing curly brace typos in Javadoc

[Archie Cobbs]

This PR fixes minor Javadoc typos in a few `java.base` classes. Extra curly braces have been sneaking in.

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Commit messages:
 - Fix minor Javadoc typos.

Changes: https://git.openjdk.org/jdk/pull/24022/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24022&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351897
  Stats: 12 lines in 5 files changed: 0 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/24022.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24022/head:pull/24022

PR: https://git.openjdk.org/jdk/pull/24022