Remove unneeded toString(QPair) declaration

It's literally the same as the std::pair one that immediately follows
it, because QPair these days is just a template alias for std::pair.

Wasn't flagged as an error because it's just a declaration, not a
definition.

Pick-to: 6.6 6.5
Change-Id: I5b47572f6e2a71edb47cbe224801a719ff1e060d
Reviewed-by: Jason McDonald <macadder1@gmail.com>

src/testlib/qtestcase.h

@@ -352,9 +352,6 @@ namespace QTest
         return Internal::toString(t);
     }
 
-    template <typename T1, typename T2>
-    inline char *toString(const QPair<T1, T2> &pair);
-
     template <typename T1, typename T2>
     inline char *toString(const std::pair<T1, T2> &pair);
 

src/testlib/qtestcase.qdoc

@@ -1363,13 +1363,6 @@
     moving the mouse pointer.
 */
 
-/*!
-    \fn template <typename T1, typename T2> char *QTest::toString(const QPair<T1, T2> &pair)
-    \overload
-    \since 5.11
-    Returns a textual representation of the \a pair.
-*/
-
 /*!
     \fn template <typename T1, typename T2> char *QTest::toString(const std::pair<T1, T2> &pair)
     \overload