updated project linter-rules and enforced them

lib/api/marianumcloud/talk/deleteMessage/deleteMessage.dart

@@ -7,7 +7,7 @@ import '../talkApi.dart';
 class DeleteMessage extends TalkApi {
   String chatToken;
   int messageId;
-  DeleteMessage(this.chatToken, this.messageId) : super("v1/chat/$chatToken/$messageId", null);
+  DeleteMessage(this.chatToken, this.messageId) : super('v1/chat/$chatToken/$messageId', null);
 
   @override
   assemble(String raw) {