RFR: 8301492: Modernize equals() method of ResourceBundle.CacheKey and Bundles.CacheKey

[Sergey Tsypanov]

`ResourceBundle.CacheKey.equals()` and `Bundles.CacheKey.equals()` are quire outdated. This simple clean-up modernizes them.

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Commit messages:
 - Copyright year update
 - Modernize Bubldes.equals()

Changes: https://git.openjdk.org/jdk/pull/12328/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12328&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301492
  Stats: 13 lines in 2 files changed: 0 ins; 4 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/12328.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12328/head:pull/12328

PR: https://git.openjdk.org/jdk/pull/12328