omni: change branch refs to 13.0

Change-Id: I07996ea076918aae2868a3e8c82d3920d9ab5b0f
diff --git a/utils/aosp-push-merge.sh b/utils/aosp-push-merge.sh
index 5ffa785..e7a27a1 100755
--- a/utils/aosp-push-merge.sh
+++ b/utils/aosp-push-merge.sh
@@ -25,7 +25,7 @@
 
 url="gerrit.omnirom.org"
 port="29418"
-branch="android-12.1"
+branch="android-13.0"
 
 cd ../../../