RFR: 8340360: Update -mx to -Xmx in UnninstallUIMemoryLeaks test

[Jaikiran Pai]

Can I please get a review of this test-only change which replaces the use of the outdated "-mx" option with the "-Xmx" option when launching the java processes in this test? This test was missed out from one of the earlier integrated PR.

The test continues to pass after this change.

-------------

Commit messages:
 - 8340360:Update -mx to -Xmx in UnninstallUIMemoryLeaks test

Changes: https://git.openjdk.org/jdk/pull/21053/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21053&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340360
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21053.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21053/head:pull/21053

PR: https://git.openjdk.org/jdk/pull/21053