Remove the changes to the debian changelog

Since this is not a full release yet

debian/changelog

@@ -1,9 +1,3 @@
-matrix-synapse-py3 (1.13.0) stable; urgency=medium
-
-  * New synapse release 1.13.0.
-
- -- Synapse Packaging team <packages@matrix.org>  Tue, 26 May 2020 14:44:07 +0000
-
 matrix-synapse-py3 (1.13.0) stable; urgency=medium
 
   [ Patrick Cloke ]