RFR: 8343891: Test javax/swing/JTabbedPane/TestJTabbedPaneBackgroundColor.java failed

[Abhishek Kumar]

TestJTabbedPaneBackgroundColor.java test was failing intermittently in CI jobs. Test is modified to access UI components on EDT for stabilizations. CI testing seems fine after test change. Link attached in JBS.

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Commit messages:
 - Test stabilization

Changes: https://git.openjdk.org/jdk/pull/24148/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24148&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343891
  Stats: 23 lines in 1 file changed: 12 ins; 3 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/24148.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24148/head:pull/24148

PR: https://git.openjdk.org/jdk/pull/24148