RFR: 8336816: runtime/PrintingTests/StringPrinting.java fails with release VMs

[Jie Fu]

Just add `-XX:+UnlockDiagnosticVMOptions` to fix the failure with release VMs.
Thanks.

-------------

Commit messages:
 - 8336816: runtime/PrintingTests/StringPrinting.java fails with release VMs

Changes: https://git.openjdk.org/jdk/pull/20249/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20249&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336816
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20249.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20249/head:pull/20249

PR: https://git.openjdk.org/jdk/pull/20249