[jdk21u-dev] RFR: 8327924: Simplify TrayIconScalingTest.java

[Goetz Lindenmaier]

I backport this for parity with 21.0.6-oracle.

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

Commit messages:
 - Backport 1496b5de9004c6a9e43ead5f6e9e88362028a7cc

Changes: https://git.openjdk.org/jdk21u-dev/pull/1133/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1133&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327924
  Stats: 27 lines in 1 file changed: 10 ins; 11 del; 6 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1133.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1133/head:pull/1133

PR: https://git.openjdk.org/jdk21u-dev/pull/1133