8329169: Parallel: Remove unused local variable in MutableSpace::print_on

Reviewed-by: tschatzl

Author: albertnetymk

src/hotspot/share/gc/parallel/mutableSpace.cpp

@@ -268,10 +268,8 @@ void MutableSpace::print_on(outputStream* st) const {
 void MutableSpace::verify() {
   HeapWord* p = bottom();
   HeapWord* t = top();
-  HeapWord* prev_p = nullptr;
   while (p < t) {
     oopDesc::verify(cast_to_oop(p));
-    prev_p = p;
     p += cast_to_oop(p)->size();
   }
   guarantee(p == top(), "end of last object must match end of space");