build(deps): bump Microsoft.Reactive.Testing from 4.4.1 to 5.0.0 in /…

…src (#648)

Bumps [Microsoft.Reactive.Testing](https://github.com/dotnet/reactive) from 4.4.1 to 5.0.0.
- [Release notes](https://github.com/dotnet/reactive/releases)
- [Commits](dotnet/reactive@rxnet-v4.4.1...ixnet-v5.0.0)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/Akavache.Tests/Akavache.Tests.csproj

@@ -9,7 +9,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.8.3" />
-    <PackageReference Include="Microsoft.Reactive.Testing" Version="4.4.1" />
+    <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.console" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />