RFR: 8354794: [TestBug] LocalDateTimeStringConverterTest: Not all Tests needs to be parameterized

[Marius Hanl]

As discussed in #1778, those test does not need to be parameterized, we therefore can replace `@ParameterizedTest` and `@MethodSource` with `@Test`.

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Commit messages:
 - 8354794: [TestBug] LocalDateTimeStringConverterTest: Not all Tests needs to be parameterized

Changes: https://git.openjdk.org/jfx/pull/1782/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1782&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354794
  Stats: 7 lines in 1 file changed: 1 ins; 3 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1782.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1782/head:pull/1782

PR: https://git.openjdk.org/jfx/pull/1782