RFR: 8270455: Remove unused JFR tracer related code in G1CollectedHeap

[Thomas Schatzl]

Hi,

  please review this unused code deletion.

Testing: local build.

Thanks,
  Thomas

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Commit messages:
 - Remove unused code

Changes: https://git.openjdk.java.net/jdk/pull/4778/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4778&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8270455
  Stats: 18 lines in 2 files changed: 0 ins; 18 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4778.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4778/head:pull/4778

PR: https://git.openjdk.java.net/jdk/pull/4778