RFR: 8311585: Add JRadioButtonMenuItem to bug8031573.java

[Rajat Mahajan]

I have made the test changes to include radio button in menu and tested the same and it works fine.

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Commit messages:
 - 8311585: Add JRadioButtonMenuItem to bug8031573.java

Changes: https://git.openjdk.org/jdk/pull/15441/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15441&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311585
  Stats: 6 lines in 1 file changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15441.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15441/head:pull/15441

PR: https://git.openjdk.org/jdk/pull/15441