RFR: 8340408: Shenandoah: Remove redundant task stats printing code in ShenandoahTaskQueue

[Zhengyu Gu]

[JDK-8280397](https://bugs.openjdk.org/browse/JDK-8280397) made the code redundant. 

Adopt shared implementation.

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Commit messages:
 - 8340408: Shenandoah: Remove redundant task stats printing code in ShenandoahTaskQueue

Changes: https://git.openjdk.org/jdk/pull/21077/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21077&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340408
  Stats: 49 lines in 4 files changed: 0 ins; 47 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21077.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21077/head:pull/21077

PR: https://git.openjdk.org/jdk/pull/21077