[pygobject] NEWS: typo

[Christoph Reiter <creiter src gnome org>]

commit 120080cf3541ed60c99d0fbb32f9c7de80a1e7c1
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Fri Nov 30 21:18:45 2018 +0100

    NEWS: typo

 NEWS | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/NEWS b/NEWS
index 931bf696..283119f2 100644
--- a/NEWS
+++ b/NEWS
@@ -2,7 +2,7 @@
 -------------------
 
 * gtk overrides: Fix rows getting inserted on the wrong level with
-  TreeStore.insert_before/inster_after if parent=None.
+  TreeStore.insert_before/insert_after if parent=None.
   :issue:`281` (3.30 regression, thanks to :user:`Cian Wilson <cianwilson>`
   for the report)