RFR: 8373983: java/util/Locale/UseOldISOCodesTest.java fails with JTREG_AOT_JDK=onestep

[Ioi Lam]

This test checks for a warning message that's printed by `sun.util.locale.BaseLocale.<clinit>` during the AOT cache training run. Because `BaseLocale` is AOT-initialized, `BaseLocale.<clinit>` is not executed when the test is running with an AOT cache, so the message is not printed. 

Since this message was already printed in the AOT training run, it's not necessary to print it again in the AOT production run. We should exclude the test case in the `JTREG_AOT_JDK=onestep` test mode.

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Commit messages:
 - 8373983: java/util/Locale/UseOldISOCodesTest.java fails with JTREG_AOT_JDK=onestep

Changes: https://git.openjdk.org/jdk/pull/28938/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28938&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373983
  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28938.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28938/head:pull/28938

PR: https://git.openjdk.org/jdk/pull/28938