Disable retyping by default.

Author: Sergey Andreenko

src/coreclr/src/jit/jitconfigvalues.h

@@ -439,7 +439,7 @@ CONFIG_INTEGER(JitSaveFpLrWithCalleeSavedRegisters, W("JitSaveFpLrWithCalleeSave
 #endif // defined(TARGET_ARM64)
 #endif // DEBUG
 
-CONFIG_INTEGER(JitDoOldStructRetyping, W("JitDoOldStructRetyping"), 1) // Allow Jit to retype structs as primitive types
+CONFIG_INTEGER(JitDoOldStructRetyping, W("JitDoOldStructRetyping"), 0) // Allow Jit to retype structs as primitive types
                                                                        // when possible.
 
 #undef CONFIG_INTEGER