RFR: 8254939: macOS: unused function 'replicate4_imm'

[Dean Long]

Removed an unused function to resolve build warnings.

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Commit messages:
 - removed unused function replicate4_imm

Changes: https://git.openjdk.java.net/jdk/pull/1643/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1643&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254939
  Stats: 13 lines in 1 file changed: 0 ins; 13 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1643.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1643/head:pull/1643

PR: https://git.openjdk.java.net/jdk/pull/1643