chore(deps): update dependency serilog.sinks.async to v2

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
Serilog.Sinks.Async (source)	1.5.0 -> 2.0.0

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Release Notes

serilog/serilog-sinks-async (Serilog.Sinks.Async)

### [`v2.0.0`](https://togithub.com/serilog/serilog-sinks-async/releases/tag/v2.0.0) - [#​85](https://togithub.com/serilog/serilog-sinks-async/issues/85) - fixed typo in README.md ([@​NielsPilgaard](https://togithub.com/NielsPilgaard)) - [#​95](https://togithub.com/serilog/serilog-sinks-async/issues/95) - update to Serilog 4, remove redundant `WriteTo.Async()` overloads, drop pre-`netstandard2.0` TFMs ([@​nblumhardt](https://togithub.com/nblumhardt))

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