[LoopUtils] Only verify SE in builds with assertions.

Follow up to 60b852092c.

llvm/lib/Transforms/Utils/LoopUtils.cpp

@@ -725,8 +725,10 @@ void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT, ScalarEvolution *SE,
     LI->destroy(L);
   }
 
+#ifndef NDEBUG
   if (SE)
     SE->verify();
+#endif
 }
 
 /// Checks if \p L has single exit through latch block except possibly