RFR: 8371682: Suppress javac warning from ThreadPoolExecutorSubclassTest.java

[SendaoYan]

Hi all,

In JDK 11, ThreadPoolExecutor.finalize() was specified to do nothing, leaving the finalize() method empty by [JDK-8371748](https://bugs.openjdk.org/browse/JDK-8371748), so I think it's safety to remove finalize() in testFinalizeMethodCallsSuperFinalize for test/jdk/java/util/concurrent/tck/ThreadPoolExecutorSubclassTest.java.

This PR also remove unnecessary '@SuppressWarnings("removal")' in test/jdk/java/util/concurrent/tck/JSR166TestCase.java and test/jdk/java/util/concurrent/tck/ExecutorsTest.java.

Change has been verified locally on linux-x64 by run test ava/util/concurrent/tck/JSR166TestCase.java#default. Test-fix only, no risk,

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Commit messages:
 - 8371682: Suppress javac warning from ThreadPoolExecutorSubclassTest.java

Changes: https://git.openjdk.org/jdk/pull/28278/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28278&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371682
  Stats: 11 lines in 3 files changed: 0 ins; 11 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28278.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28278/head:pull/28278

PR: https://git.openjdk.org/jdk/pull/28278