[PM-10440] Enable minification on beta build variants (#3661)

app/build.gradle.kts

@@ -65,8 +65,13 @@ android {
 
         // Beta and Release variants are identical except beta has a different package name
         create("beta") {
-            initWith(buildTypes.getByName("release"))
             applicationIdSuffix = ".beta"
+            isDebuggable = false
+            isMinifyEnabled = true
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro"
+            )
         }
         release {
             isDebuggable = false