RFR: 8375567: Remove AppContext usage from Swing Motif L&F classes

[Phil Race]

Remove AppContext from the Swing Motif L&F implementation.

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Commit messages:
 - 8375567

Changes: https://git.openjdk.org/jdk/pull/29282/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29282&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375567
  Stats: 45 lines in 5 files changed: 0 ins; 36 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/29282.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29282/head:pull/29282

PR: https://git.openjdk.org/jdk/pull/29282