make social provider a final class

Author: navaronbracke

lib/src/models/enums/social_provider.dart

@@ -1,9 +1,7 @@
-// TODO: investigate if this can be a `final class` once Class Modifiers are available in Dart 3.0
-
 /// The currently supported social providers.
 ///
-/// Depending on the platform; some social providers might be unavailable.
-class SocialProvider {
+/// Depending on the platform, some social providers might be unavailable.
+final class SocialProvider {
   /// The private constructor.
   const SocialProvider._(this.name);