Fixed code indentation, numbering and typo in Discussion: Destructors, deallocation, and swap must never fail

CppCoreGuidelines.md

@@ -12971,7 +12971,7 @@ Here, copying `s` could throw, and if that throws and if `n`'s destructor then a
         void test(string& s)
         {
             innocent_bystander i; // more trouble brewing
-        string copy = s;      // copy the string
+            string copy2 = s;      // copy the string
         } // destroy copy and then i
 
     Here, if constructing `copy2` throws, we have the same problem because `i`'s destructor now also can throw, and if so we'll invoke `std::terminate`.