RFR: 8371771: CDS test SharedStringsStress.java failed with insufficient heap

[Ioi Lam]

Please review this trivial fix. The test requires more initial heap space than the default settings of *some* of our test hosts, so it fails intermittently.

The fix is to specify a large enough `-Xms` (128 MB).

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Commit messages:
 - 8371771: CDS test SharedStringsStress.java failed with insufficient heap

Changes: https://git.openjdk.org/jdk/pull/28379/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28379&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371771
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28379.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28379/head:pull/28379

PR: https://git.openjdk.org/jdk/pull/28379