[babl] docs: remove todo item referring to CMYK

[Øyvind "pippin" Kolås <ok src gnome org>]

commit c66383b670e32e165c3771bd694d118c5d57ec01
Author: Øyvind Kolås <pippin gimp org>
Date:   Sun Dec 2 19:31:45 2018 +0100

    docs: remove todo item referring to CMYK

 TODO | 1 -
 1 file changed, 1 deletion(-)
---
diff --git a/TODO b/TODO
index 843cef1..2dbb27a 100644
--- a/TODO
+++ b/TODO
@@ -1,6 +1,5 @@
 <h2>TODO</h2>
 
 <ul>
-  <li>Support for conversions between formats that have higher dimensionality than RGBA.</li>
   <li>Support for datatypes that are not a multiple of 8bit.</li>
 </ul>