Remove @since annotations for new Scintilla GetDirectXXX() methods

This partially undoes 0a3057b83c which wrongly
modified the generated interface/wx/stc/stc.h file, as these changes were lost
after regenerating it again.

Unfortunately it doesn't seem possible to have @since annotations for the
Scintilla methods currently, ideally the generator script should be modified
to allow this, somehow.

See #17481.

interface/wx/stc/stc.h

@@ -4021,16 +4021,12 @@ public:
 
     /**
         Retrieve a pointer to a function that processes messages for this Scintilla.
-
-        @since 3.1.1
     */
     void* GetDirectFunction() const;
 
     /**
         Retrieve a pointer value to use as the first argument when calling
         the function returned by GetDirectFunction.
-
-        @since 3.1.1
     */
     void* GetDirectPointer() const;