8318649: G1: Remove unimplemented HeapRegionRemSet::add_code_root_locked

Reviewed-by: tschatzl

src/hotspot/share/gc/g1/heapRegionRemSet.hpp

@@ -149,7 +149,6 @@ public:
   // Routines for managing the list of code roots that point into
   // the heap region that owns this RSet.
   void add_code_root(nmethod* nm);
-  void add_code_root_locked(nmethod* nm);
   void remove_code_root(nmethod* nm);
 
   // Applies blk->do_code_blob() to each of the entries in _code_roots