[jdk17] RFR: 8268080: java/util/concurrent/forkjoin/AsyncShutdownNow.java fails with java.util.concurrent.RejectedExecutionException

[Julia Boes]

In the methods in question, `RejectedExecutionException` is an expected exception that was previously unhandled (it is a `RuntimeException`, not a subclass of `ExecutionException`). This change adds `RejectedExecutionException` to the existing catch clause.

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Commit messages:
 - initial change

Changes: https://git.openjdk.java.net/jdk17/pull/74/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=74&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268080
  Stats: 8 lines in 2 files changed: 2 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/74.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/74/head:pull/74

PR: https://git.openjdk.java.net/jdk17/pull/74