RFR: 8365572: Shenandoah: Remove unused thread local _paced_time field

[William Kemper]

We missed this spot when removing the ShenandoahPacer.

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Commit messages:
 - Remove unused ShenandoahThreadLocalData::_paced_time

Changes: https://git.openjdk.org/jdk/pull/26788/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26788&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365572
  Stats: 15 lines in 2 files changed: 0 ins; 15 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26788.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26788/head:pull/26788

PR: https://git.openjdk.org/jdk/pull/26788