RFR: 8297296: java/awt/Mouse/EnterExitEvents/DragWindowTest.java fails with "No MouseReleased event on label!"

[Alisen Chung]

Test was run on mac, windows, linux 50 times and passed after change
Before fix, test fails about once every 50 runs on linux and windows platforms

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Commit messages:
 - changed robot autodelay to 250

Changes: https://git.openjdk.org/jdk/pull/11425/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11425&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297296
  Stats: 3 lines in 2 files changed: 1 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/11425.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11425/head:pull/11425

PR: https://git.openjdk.org/jdk/pull/11425