Upgrade sd_notify to 0.1.1
Current version 0.1.0 doesn't have any tests. 0.1.1 is just a patch with tests included in the release with minimal source code change https://github.com/agis/ruby-sdnotify/releases/tag/v0.1.1
Changes: https://github.com/agis/ruby-sdnotify/compare/v0.1.0...v0.1.1
Latest commit in master has passing CI against Ruby 3 (which is technically the same source code as v0.1.1)