[jdk21u-dev] RFR: 8346234: javax/swing/text/DefaultEditorKit/4278839/bug4278839.java still fails in CI

[Goetz Lindenmaier]

I backport this for parity with 21.0.10-oracle.

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Commit messages:
 - Backport 466c00ac88569d145a47845b2c9a2522a1649889

Changes: https://git.openjdk.org/jdk21u-dev/pull/2303/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2303&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346234
  Stats: 59 lines in 1 file changed: 45 ins; 0 del; 14 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2303.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2303/head:pull/2303

PR: https://git.openjdk.org/jdk21u-dev/pull/2303