Revert "Bug 741959 - text input broken on OS X 10.5 from 2.24.19 onwards"

This reverts commit 4d1c065 because with further testing it's found that
imquartz works on Leopard without it and is broken with it.

gdk/quartz/GdkQuartzView.c

@@ -186,15 +186,7 @@
     [self performSelector: aSelector];
 }
 
-/* This gets called on OS X 10.6 and upwards from interpretKeyEvents */
 -(void)insertText: (id)aString replacementRange: (NSRange)replacementRange
-{
-  [self insertText:aString];
-}
-
-/* This gets called on OS X 10.5 from interpretKeyEvents, although 10.5
- * is supposed to support NSTextInputClient  */
--(void)insertText: (id)aString
 {
   GDK_NOTE (EVENTS, g_print ("insertText\n"));
   const char *str;