RFR: 8342787: Move misplaced TestTemplateAssertionPredicateWithTwoUCTs.java from src to test directory

[Christian Hagedorn]

For some unknown reason, `TestTemplateAssertionPredicateWithTwoUCTs.java` ended up in the src directory instead of the test directory with [JDK-8342287](https://bugs.openjdk.org/browse/JDK-8342787). Maybe a patch application have gone wrong when moving the test to another checked out JDK repository. Anyway, this patch moves it to the correct place.

Thanks to @TheShermanTanker for spotting this!

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Commit messages:
 - 8342787: Move misplaced TestTemplateAssertionPredicateWithTwoUCTs.java from src to test directory

Changes: https://git.openjdk.org/jdk/pull/21629/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21629&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342787
  Stats: 3 lines in 1 file changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21629.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21629/head:pull/21629

PR: https://git.openjdk.org/jdk/pull/21629