Bump System.Linq.Async from 4.0.0 to 4.1.1 (#147)

Bumps [System.Linq.Async](https://github.com/dotnet/reactive) from 4.0.0 to 4.1.1.
- [Release notes](https://github.com/dotnet/reactive/releases)
- [Commits](dotnet/reactive@ixnet-v4.0.0...ixnet-v4.1.1)

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Author: dependabot-preview[bot]

Tests/Boxed.Mapping.Test/Boxed.Mapping.Test.csproj

@@ -9,7 +9,7 @@
   </ItemGroup>
 
   <ItemGroup Label="Package References">
-    <PackageReference Include="System.Linq.Async" Version="4.0.0" />
+    <PackageReference Include="System.Linq.Async" Version="4.1.1" />
   </ItemGroup>
 
   <ItemGroup>