RFR: 8378192: Remove AppContext from SwingUtilities2

[Phil Race]

Remove AppContext from SwingUtilities2

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Commit messages:
 - 8378192

Changes: https://git.openjdk.org/jdk/pull/29798/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29798&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378192
  Stats: 11 lines in 1 file changed: 0 ins; 10 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29798.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29798/head:pull/29798

PR: https://git.openjdk.org/jdk/pull/29798