RFR: 8365622: Shenandoah: Fix Shenandoah simple bit map test

[William Kemper]

Simple fix. Test passes.

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Commit messages:
 - Use right macro too
 - Use correct class name for test fixture

Changes: https://git.openjdk.org/jdk/pull/26805/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26805&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365622
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26805.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26805/head:pull/26805

PR: https://git.openjdk.org/jdk/pull/26805