d/gbp.conf: Return to debian/master branch

debian/changelog

@@ -1,5 +1,6 @@
 ostree (2019.2-2) UNRELEASED; urgency=medium
 
+  * d/gbp.conf: Return to debian/master branch
   * d/salsa-ci.yml: Request standard CI on salsa.debian.org
     - Disable build-time tests with DEB_BUILD_OPTIONS=nocheck for now.
       They don't currently work in the salsa-ci infrastructure, but I

debian/gbp.conf

@@ -1,7 +1,7 @@
 [DEFAULT]
 pristine-tar = True
 compression = xz
-debian-branch = debian/experimental
+debian-branch = debian/master
 upstream-branch = upstream/latest
 patch-numbers = False
 upstream-vcs-tag = v%(version)s