<i18n dev> RFR: 8177352: Calendar.getDisplayName(s) in non-lenient mode inconsistent, does not match spec

[Justin Lu]

This PR updates the javadoc of `java.util.Calendar.getDisplayName()` and `java.util.Calendar.getDisplayNames()` to better reflect the actual behavior when the calendar is non-lenient.

This involves adding the **implSpec** tag to both methods to clarify behavior, as well as removing false behavior from the **throws** tag in `java.util.Calendar.getDisplayNames()`.

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Commit messages:
 - Adjust wording of spec for getDisplayName()
 - Copyright year
 - Change to normal spec changes (as opposed to implSpec)
 - JDK-8177352

Changes: https://git.openjdk.org/jdk/pull/13083/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13083&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8177352
  Stats: 16 lines in 1 file changed: 12 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13083.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13083/head:pull/13083

PR: https://git.openjdk.org/jdk/pull/13083