RFR: 8302121: Parallel: Remove unused arg in PSCardTable::inline_write_ref_field_gc

[Albert Mingkun Yang]

Trivial removing dead code.

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Commit messages:
 - trivial

Changes: https://git.openjdk.org/jdk/pull/12485/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12485&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302121
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12485.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12485/head:pull/12485

PR: https://git.openjdk.org/jdk/pull/12485