[jdk21u] RFR: 8311026: Some G1 specific tests do not set -XX:+UseG1GC

[Matthias Baesken]

8311026: Some G1 specific tests do not set -XX:+UseG1GC

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Commit messages:
 - Backport a7d168b522bb05345a40ae1fb18942ba663d3182

Changes: https://git.openjdk.org/jdk21u/pull/18/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=18&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311026
  Stats: 4 lines in 3 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk21u/pull/18.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/18/head:pull/18

PR: https://git.openjdk.org/jdk21u/pull/18