Bump Serilog.Sinks.Graylog from 2.1.3 to 2.2.1
Bumps [Serilog.Sinks.Graylog](https://github.com/whir1/serilog-sinks-graylog) from 2.1.3 to 2.2.1.
- [Release notes](https://github.com/whir1/serilog-sinks-graylog/releases)
- [Commits](https://github.com/whir1/serilog-sinks-graylog/commits)
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