RFR: 8282381: Parallel: Remove unnecessary PCReferenceProcessor

[Albert Mingkun Yang]

Simple change of removing a redundant class.

Test: tier1-5

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Commit messages:
 - ps-ref-discover

Changes: https://git.openjdk.java.net/jdk/pull/7618/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7618&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282381
  Stats: 32 lines in 1 file changed: 3 ins; 27 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7618.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7618/head:pull/7618

PR: https://git.openjdk.java.net/jdk/pull/7618