Enable Element Call integration in rooms by default (#1685)

Also change base url to `call.element.dev`.

libraries/featureflag/test/src/main/java/io/element/android/libraries/featureflag/test/FakeFeatureFlagService.kt

@@ -31,6 +31,6 @@ class FakeFeatureFlagService(
     }
 
     override suspend fun isFeatureEnabled(feature: Feature): Boolean {
-        return enabledFeatures[feature.key] ?: feature.defaultValue
+        return enabledFeatures[feature.key] ?: false
     }
 }