Please review this PR which is a continuation of [JDK-6453901](https://bugs.openjdk.org/browse/JDK-6453901) to remove unused code from the _sun.util.Calendar_ classes.
`forceStandardTime` is always false. In addition, `locale` is never by used by _CalendarDate_ or any inheritors and can be removed. As a result, _ImmutableGregorianDate_ no longer needs to override the _setLocale_ method and throw UnsupportedOperationException. ------------- Commit messages: - init Changes: https://git.openjdk.org/jdk/pull/15726/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15726&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8313813 Stats: 14 lines in 2 files changed: 0 ins; 13 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/15726.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/15726/head:pull/15726 PR: https://git.openjdk.org/jdk/pull/15726
