RFR: 8266784: java/text/Collator/RuleBasedCollatorTest.java fails with jtreg 6

[Naoto Sato]

Please review this test case fix for the upcoming jtreg 6. The test was using `@BeforeGroups` annotation, and the behavior of it has changed in TestNG 7.1 so that it is only issued when the test was configured with filtering. Changed to use `@BeforeClass` instead.

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Commit messages:
 - 8266784: java/text/Collator/RuleBasedCollatorTest.java fails with jtreg 6

Changes: https://git.openjdk.java.net/jdk/pull/3959/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3959&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266784
  Stats: 8 lines in 1 file changed: 0 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3959.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3959/head:pull/3959

PR: https://git.openjdk.java.net/jdk/pull/3959