RFR: 8327522: Shenandoah: Remove unused references to satb_mark_queue_active_offset

[Yude Lin]

Removed an unused variable (trivial)

Also, there is another place that uses satb_mark_queue_active_offset which is ShenandoahBarrierSetC2::verify_gc_barriers
The current barrier pattern is different from what this code is expecting:
If->Bool->CmpI->AndI->LoadUB->AddP->ConL(gc_state_offset)
rather than
If->Bool->CmpI->LoadB->AddP->ConL(marking_offset)
However, this code isn't doing as much checking as its counterpart in G1 anyway (so I'm thinking removing the incorrect matching code altogether?) Looking forward to your suggestions.

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Commit messages:
 - 8327522: Shenandoah: Remove unused references to satb_mark_queue_active_offset

Changes: https://git.openjdk.org/jdk/pull/18148/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18148&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327522
  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18148.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18148/head:pull/18148

PR: https://git.openjdk.org/jdk/pull/18148