RFR: 8310037: Leak MutableSpaceUsedHelper in parallel GC's SpaceCounters class

[Zhengyu Gu]

Please review this small fix for memory leak.

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Commit messages:
 - update copyright year
 - 8310037: Leak MutableSpaceUsedHelper in parallel GC's SpaceCounters class

Changes: https://git.openjdk.org/jdk/pull/14472/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14472&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310037
  Stats: 10 lines in 2 files changed: 6 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/14472.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14472/head:pull/14472

PR: https://git.openjdk.org/jdk/pull/14472