Add wxStyledTextCtrl::SelectNone() to the template header file too.

This method was only added to the generated include/wx/stc/stc.h but not to
src/stc/stc.h.in from which it is created in r72490, do update the latter file
too now.

See #12960.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72517 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/stc/stc.h.in

@@ -329,6 +329,11 @@ public:
         }
     }
 
+    virtual void SelectNone()
+    {
+        ClearSelections();
+    }
+
 #ifdef SWIG
     void GetSelection(long* OUTPUT, long* OUTPUT) const;
 #else