RFR: 8351456: Build failure with --disable-jvm-feature-shenandoahgc after 8343468

[Martin Doerr]

Fix Shenandoah exclusion. Tested on aarch64, not on riscv.

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

Commit messages:
 - 8351456: Build failure with --disable-jvm-feature-shenandoahgc after 8343468

Changes: https://git.openjdk.org/jdk/pull/23955/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23955&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351456
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23955.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23955/head:pull/23955

PR: https://git.openjdk.org/jdk/pull/23955