release: prepare version number for beta releases

set track to beta as I was going to promote it immediately anyway
by my reading, this will "supersede" the "closed testing" track
(which we call "alpha") because it's a higher version code, and those
users will be served the APKs we push to beta (and production) until
we start up 2.22alpha track

Author: mikehardy

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=22100122
-        versionName="2.21alpha22"
+        versionCode=22100200
+        versionName="2.21.0beta0"
         minSdk = libs.versions.minSdk.get().toInteger()
 
         // After #13695: change .tests_emulator.yml
@@ -264,7 +264,7 @@ android {
 
 play {
     serviceAccountCredentials.set(file("${homePath}/src/AnkiDroid-GCP-Publish-Credentials.json"))
-    track.set('alpha')
+    track.set('beta')
 
     // any time we bump minSdk we want Play Store to retain the old artifacts by version code,
     // so that they remain available for older devices