RFR: 8333940: Ensure javax/swing/TestUngrab.java run on all platforms

[Prasanta Sadhukhan]

TestUngrab.java was added for [JDK-8267374](https://bugs.openjdk.org/browse/JDK-8267374) macos fix but the test can be run for all platforms as the behaviour is common for all
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Commit messages:
 - Test-fix

Changes: https://git.openjdk.org/jdk/pull/19644/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19644&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333940
  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/19644.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19644/head:pull/19644

PR: https://git.openjdk.org/jdk/pull/19644