release: prepare for 2.20 with 2.20.0beta1

setting release number to 0 first lets the auto-increment take it to 1
in the release script

setting it to beta channel as I was going to promote it immediately anyway

AnkiDroid/build.gradle

@@ -85,8 +85,8 @@ android {
         //
         // This ensures the correct ordering between the various types of releases (dev < alpha < beta < release) which is
         // needed for upgrades to be offered correctly.
-        versionCode=22000103
-        versionName="2.20alpha3"
+        versionCode=22000200
+        versionName="2.20.0beta0"
         minSdk libs.versions.minSdk.get().toInteger()
 
         // After #13695: change .tests_emulator.yml
@@ -255,7 +255,7 @@ android {
 
 play {
     serviceAccountCredentials.set(file("${homePath}/src/AnkiDroid-GCP-Publish-Credentials.json"))
-    track.set('alpha')
+    track.set('beta')
 }
 
 // Install Git pre-commit hook for Ktlint