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

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

libraries/featureflag/api/src/main/kotlin/io/element/android/libraries/featureflag/api/FeatureFlags.kt

@@ -59,7 +59,7 @@ enum class FeatureFlags(
         key = "feature.elementcall",
         title = "Element call in rooms",
         description = "Allow user to start or join a call in a room",
-        defaultValue = false,
+        defaultValue = true,
     ),
     Mentions(
         key = "feature.mentions",