RFR: 8367651: Parallel: Remove workers number checking in constructor of PSAdjustTask

[Albert Mingkun Yang]

Uniform thread claiming path for different number of workers.

Test: tier1-3

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Commit messages:
 - pgc-remove-if

Changes: https://git.openjdk.org/jdk/pull/27290/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27290&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367651
  Stats: 3 lines in 1 file changed: 0 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27290.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27290/head:pull/27290

PR: https://git.openjdk.org/jdk/pull/27290