RFR: 8253026: Remove dummy call to gc alot from VM Thread

[Robbin Ehn]

GC Alot can only be performed by a Java Thread:

void InterfaceSupport::gc_alot() {
  Thread *thread = Thread::current();
  if (!thread->is_Java_thread()) return; // Avoid concurrent calls

Lets remove the dummy call from the VM thread.

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Commit messages:
 - Removed code

Changes: https://git.openjdk.java.net/jdk/pull/113/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=113&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253026
  Stats: 3 lines in 1 file changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/113.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/113/head:pull/113

PR: https://git.openjdk.java.net/jdk/pull/113