simplified code across the app and consolidated duplicated helpers

lib/api/marianumcloud/talk/chat/get_chat.dart

@@ -1,6 +1,3 @@
-import 'package:http/http.dart' as http;
-import 'package:http/http.dart';
-
 import '../../nextcloud_ocs.dart';
 import '../talk_api.dart';
 import 'get_chat_params.dart';
@@ -16,11 +13,4 @@ class GetChat extends TalkApi<GetChatResponse> {
   @override
   GetChatResponse assemble(String raw) =>
       GetChatResponse.fromJson(NextcloudOcs.decode(raw));
-
-  @override
-  Future<Response> request(
-    Uri uri,
-    Object? body,
-    Map<String, String>? headers,
-  ) => http.get(uri, headers: headers);
 }