Don't delete templated function when no other overload is possible.

The compiler will produce error anyway, because the body of the function
is not implemented, only in explicit template specializations. Deleting
the function would make sense if there was another function with the
same name taking different argument, which is not this case anyway.

src/Query.h

@@ -59,7 +59,7 @@ class MAGNUM_EXPORT AbstractQuery {
          *
          * @requires_gl33 Extension <tt>ARB_timer_query</tt> (64bit integers)
          */
-        template<class T> T result() = delete;
+        template<class T> T result();
 
     protected:
         GLuint query; /**< @brief OpenGL internal query ID */