RFR: 8376747: Remove AppContext from Swing LayoutStyle

[Phil Race]

A small one. No tests fail with this removal.

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Commit messages:
 - 8376747

Changes: https://git.openjdk.org/jdk/pull/29492/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29492&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376747
  Stats: 9 lines in 1 file changed: 3 ins; 2 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/29492.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29492/head:pull/29492

PR: https://git.openjdk.org/jdk/pull/29492