Revert "GC experiment."

This reverts commit b3fb1d08137ead7b6be016e1bc147cb781e76111.
diff --git a/vm/Init.cpp b/vm/Init.cpp
index abca711..404a63d 100644
--- a/vm/Init.cpp
+++ b/vm/Init.cpp
@@ -1057,6 +1057,8 @@
     gDvm.heapGrowthLimit = 0;  // 0 means no growth limit
     gDvm.stackSize = kDefaultStackSize;
 
+    gDvm.concurrentMarkSweep = true;
+
     /* gDvm.jdwpSuspend = true; */
 
     /* allowed unless zygote config doesn't allow it */