common_types: Specify const in deleted copy constructor/assignment operator

src/common/common_types.h

@@ -56,6 +56,6 @@ protected:
     NonCopyable() = default;
     ~NonCopyable() = default;
 
-    NonCopyable(NonCopyable&) = delete;
-    NonCopyable& operator=(NonCopyable&) = delete;
+    NonCopyable(const NonCopyable&) = delete;
+    NonCopyable& operator=(const NonCopyable&) = delete;
 };