Add the mandatory override specifier to make clang-tidy happy

src/map.h

@@ -1843,6 +1843,6 @@ class fake_map : public tinymap
     public:
         fake_map( const furn_id &fur_type, const ter_id &ter_type, const trap_id &trap_type,
                   int fake_map_z );
-        ~fake_map();
+        ~fake_map() override;
 };
 #endif