RFR: 8378197: Remove AppContext from sun/swing/plaf/DesktopProperty.java

[Phil Race]

A straightforward removal of a per-AppContext flag which can now be static

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Commit messages:
 - 8378197

Changes: https://git.openjdk.org/jdk/pull/29801/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29801&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378197
  Stats: 9 lines in 1 file changed: 2 ins; 4 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/29801.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29801/head:pull/29801

PR: https://git.openjdk.org/jdk/pull/29801