RFR: JDK-8266794: Remove dead code notify_allocation_jvmti_allocation_event

[Hamlin Li]

This is a trivial change to remove some dead code related to jvmti in gc.

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Commit messages:
 - Merge branch 'openjdk:master' into remove-jvmti
 - JDK-8266794: remove dead code notify_allocation_jvmti_allocation_event

Changes: https://git.openjdk.java.net/jdk/pull/3963/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3963&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266794
  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3963.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3963/head:pull/3963

PR: https://git.openjdk.java.net/jdk/pull/3963