RFR: 8266299: ProblemList runtime/stringtable/StringTableCleaningTest.java on linux-aarch64 with ZGC

[Daniel D.Daugherty]

A trivial fix to ProblemList runtime/stringtable/StringTableCleaningTest.java on linux-aarch64 with ZGC.

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Commit messages:
 - 8266299: ProblemListruntime/stringtable/StringTableCleaningTest.java on linux-aarch64 with ZGC

Changes: https://git.openjdk.java.net/jdk/pull/3797/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3797&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266299
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3797.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3797/head:pull/3797

PR: https://git.openjdk.java.net/jdk/pull/3797