[fenix] Bug 1807933 - Enable places storage maintenance feature for the Beta variant.

Places storage maintenance flag is enabled for the Beta variant, previously it was enabled only for Nightly variant. This feature registers a periodic storage maintenance worker that runs to prune and maintain places db.

app/src/main/java/org/mozilla/fenix/FeatureFlags.kt

@@ -72,5 +72,5 @@ object FeatureFlags {
      *
      * Feature flag tracking: https://github.com/mozilla-mobile/fenix/issues/27759
      * */
-    val storageMaintenanceFeature = Config.channel.isNightlyOrDebug
+    val storageMaintenanceFeature = Config.channel.isNightlyOrDebug || Config.channel.isBeta
 }