patch checklist:Remove pointless checkheaders comment, its just a waste of time

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/developer.texi

@@ -320,8 +320,6 @@ send a reminder by email. Your patch should eventually be dealt with.
 @enumerate
 @item
     Do the regression tests pass with the patch applied?
-@item
-    Does @code{make checkheaders} pass with the patch applied?
 @item
     Is the patch a unified diff?
 @item