Unused baseUrl parameter warning fix (#677)

#676 I am passing baseUrl through @RESTapi, it is showing a warning that I am not using the baseUrl parameter from the Auto-generated(g.dart) file

With the following comment, this issue can be resolved
// ignore_for_file: unused_element

generator/lib/src/generator.dart

@@ -16,7 +16,7 @@ import 'package:source_gen/source_gen.dart';
 import 'package:tuple/tuple.dart';
 
 const _analyzerIgnores =
-    '// ignore_for_file: unnecessary_brace_in_string_interps,no_leading_underscores_for_local_identifiers';
+    '// ignore_for_file: unnecessary_brace_in_string_interps,no_leading_underscores_for_local_identifiers,unused_element';
 
 class RetrofitOptions {
   RetrofitOptions({