Remove unused global memoryAllocMonitor definition

The global memoryAllocMonitor is no longer used by the persistent
allocator in OpenJ9, hence its definition in OMR can now be removed.

Signed-off-by: Alexey Khrabrov <khrabrov@cs.toronto.edu>

compiler/env/TRPersistentMemory.cpp

@@ -40,7 +40,6 @@
 namespace TR { class Compilation; }
 namespace TR { class PersistentInfo; }
 
-extern TR::Monitor *memoryAllocMonitor;
 extern const char * objectName[];
 
 namespace TR

compiler/infra/OMRMonitor.cpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2018 IBM Corp. and others
+ * Copyright (c) 2000, 2021 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -29,8 +29,6 @@
 
 TR::MonitorTable *OMR::MonitorTable::_instance = 0;
 
-TR::Monitor *memoryAllocMonitor = NULL;
-
 void *
 OMR::Monitor::operator new(size_t size)
    {

compiler/infra/OMRMonitorTable.hpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2019 IBM Corp. and others
+ * Copyright (c) 2000, 2021 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -46,7 +46,6 @@ class OMR_EXTENSIBLE MonitorTable
    void free() { TR_UNIMPLEMENTED(); }
    void removeAndDestroy(TR::Monitor *monitor) { TR_UNIMPLEMENTED(); }
 
-   TR::Monitor *getMemoryAllocMonitor() { return _memoryAllocMonitor; }
    TR::Monitor *getScratchMemoryPoolMonitor() { return _scratchMemoryPoolMonitor; }
 
    protected:
@@ -55,10 +54,6 @@ class OMR_EXTENSIBLE MonitorTable
 
    static TR::MonitorTable *_instance;
 
-   // Used by TR_PersistentMemory
-   //
-   TR::Monitor *_memoryAllocMonitor;
-
    // Used by SCRATCH segments allocations
    // A copy of this goes into TR_PersistentMemory as well
    //