RFR: 8371321: Remove unused last arg of BarrierSetAssembler::arraycopy_epilogue

[Albert Mingkun Yang]

Removing effectively dead code.

Test: tier1, GHA

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Commit messages:
 - remove-barrier-arg

Changes: https://git.openjdk.org/jdk/pull/28146/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28146&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371321
  Stats: 38 lines in 16 files changed: 0 ins; 6 del; 32 mod
  Patch: https://git.openjdk.org/jdk/pull/28146.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28146/head:pull/28146

PR: https://git.openjdk.org/jdk/pull/28146