RFR: 8376432: Remove AppContext from sun/swing/DefaultLookup.java

[Phil Race]

Another removal of AppContext in Swing

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

Commit messages:
 - 8376432

Changes: https://git.openjdk.org/jdk/pull/29439/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29439&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376432
  Stats: 40 lines in 1 file changed: 1 ins; 28 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/29439.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29439/head:pull/29439

PR: https://git.openjdk.org/jdk/pull/29439