[func.wrap.func] Remove redundant declarations of swap and op== (#4411)

The declarations of the non-member functions swap and operator==
are already present in the header synopsis [functional.syn] and do not
need to be repeated in the class synopsis.

Author: JohelEGP

source/utilities.tex

@@ -13150,9 +13150,11 @@
   template<class> class function;       // \notdef
   template<class R, class... ArgTypes> class function<R(ArgTypes...)>;
 
+  // \ref{func.wrap.func.alg}, specialized algorithms
   template<class R, class... ArgTypes>
     void swap(function<R(ArgTypes...)>&, function<R(ArgTypes...)>&) noexcept;
 
+  // \ref{func.wrap.func.nullptr}, null pointer comparison operator functions
   template<class R, class... ArgTypes>
     bool operator==(const function<R(ArgTypes...)>&, nullptr_t) noexcept;
 
@@ -15067,14 +15069,6 @@
     function(R(*)(ArgTypes...)) -> function<R(ArgTypes...)>;
 
   template<class F> function(F) -> function<@\seebelow@>;
-
-  // \ref{func.wrap.func.nullptr}, null pointer comparison operator functions
-  template<class R, class... ArgTypes>
-    bool operator==(const function<R(ArgTypes...)>&, nullptr_t) noexcept;
-
-  // \ref{func.wrap.func.alg}, specialized algorithms
-  template<class R, class... ArgTypes>
-    void swap(function<R(ArgTypes...)>&, function<R(ArgTypes...)>&) noexcept;
 }
 \end{codeblock}