ci: release ignore file (??)

[vincenzopalazzo]

Generate file cause following error

NullSafetyCompliance.compliant
Package validation found the following errors:
* line 10, column 1 of lib/src/generated/node.pb.dart: This package does not have fixnum in the `dependencies` section of `pubspec.yaml`.
     ╷
  10 │ import 'package:fixnum/fixnum.dart' as $fixnum;
     │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     ╵
* line 10, column 1 of lib/src/generated/primitives.pb.dart: This package does not have fixnum in the `dependencies` section of `pubspec.yaml`.