RFR: 8316328: Shenandoah: jdk/jfr/event/oldobject/TestSanityDefault.java times out for some heap sizes

[Sergey Bylokhov]

This is a request to limit the memory used by the test, otherwise it could run "forever" on huge heaps.

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Commit messages:
 - Update TestSanityDefault.java
 - 8316328: Shenandoah: jdk/jfr/event/oldobject/TestSanityDefault.java times out for some heap sizes

Changes: https://git.openjdk.org/jdk/pull/19163/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19163&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316328
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19163.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19163/head:pull/19163

PR: https://git.openjdk.org/jdk/pull/19163