RFR: 8354702: [TestBug] LocalDateTimeStringConverterTest Workaround can be removed

[Marius Hanl]

[JDK-8297316](https://bugs.openjdk.org/browse/JDK-8297316) added a Workaround for the Japanese Date Converter, which is different on JDK20 and newer. Since our Boot JDK is Java 22 as of April 2025, we can remove the workaround.

We should also consider testing and closing: [JDK-8265727](https://bugs.openjdk.org/browse/JDK-8265727) and [JDK-8141350](https://bugs.openjdk.org/browse/JDK-8141350), which seems to work fine for me (German Locale, Test correctly changes that).

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Commit messages:
 - 8354702: LocalDateTimeStringConverterTest Workaround can be removed

Changes: https://git.openjdk.org/jfx/pull/1778/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1778&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354702
  Stats: 12 lines in 1 file changed: 0 ins; 10 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/1778.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1778/head:pull/1778

PR: https://git.openjdk.org/jfx/pull/1778