[gmime] Update TODO

[Jeffrey Stedfast <fejj src gnome org>]

commit e648d8bd8474981bcddd65623772e36f42abf046
Author: Jeffrey Stedfast <jestedfa microsoft com>
Date:   Sun Mar 12 16:05:19 2017 -0400

    Update TODO

 TODO |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)
---
diff --git a/TODO b/TODO
index c4d1d2f..6f2142a 100644
--- a/TODO
+++ b/TODO
@@ -6,9 +6,6 @@ tasks are presented in.
 GMime 3.0 Planning:
 ===================
 
-- Replace prepend/append/set_header() virtual methods with event callbacks from
-  GMimeHeaderList changed events like MimeKit does things.
-
 
 Future Planning:
 ================