[non-copyable] remove empty destructor per style guide (#5401)

src/core/common/non_copyable.hpp

@@ -37,14 +37,13 @@
 namespace ot {
 
 /**
- * This class makes any class that derives from it non-copyable. It is
- * intended to be used as a private base class.
+ * This class makes any class that derives from it non-copyable. It is intended to be used as a private base class.
+ *
  */
 class NonCopyable
 {
 protected:
     NonCopyable(void) {}
-    ~NonCopyable(void) {}
 
 private:
     NonCopyable(const NonCopyable &);