Update dependency Serilog.Sinks.Async to v1.5.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
Serilog.Sinks.Async (source)	nuget	minor	1.4.0 -> 1.5.0

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Release Notes

serilog/serilog-sinks-async

### [`v1.5.0`](https://togithub.com/serilog/serilog-sinks-async/releases/v1.5.0) - [#​50](https://togithub.com/serilog/serilog-sinks-async/issues/50) - fix package license declaration ([@​nblumhardt](https://togithub.com/nblumhardt)) - [#​55](https://togithub.com/serilog/serilog-sinks-async/issues/55) - README updates ([@​thiagograndesso](https://togithub.com/thiagograndesso)) - [#​70](https://togithub.com/serilog/serilog-sinks-async/issues/70) - bump Serilog dependency to 2.9.0 to better support Unity ([@​bdovaz](https://togithub.com/bdovaz)) - [#​71](https://togithub.com/serilog/serilog-sinks-async/issues/71) - `` ([@​Numpsy](https://togithub.com/Numpsy))

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