Revert "don't use write barriers for frozen objects (dotnet#76135)"

This reverts commit 315bdd4.

Author: jkotas

src/coreclr/jit/gcinfo.cpp

@@ -252,12 +252,6 @@ GCInfo::WriteBarrierForm GCInfo::gcIsWriteBarrierCandidate(GenTreeStoreInd* stor
         return WBF_NoBarrier;
     }
 
-    if (store->Data()->IsIconHandle(GTF_ICON_OBJ_HDL))
-    {
-        // Ignore frozen objects
-        return WBF_NoBarrier;
-    }
-
     WriteBarrierForm wbf = gcWriteBarrierFormFromTargetAddress(store->Addr());
 
     if (wbf == WBF_BarrierUnknown)