Bump FsUnit from 4.0.5 to 4.0.6

Bumps [FsUnit](https://github.com/fsprojects/FsUnit) from 4.0.5 to 4.0.6.
- [Release notes](https://github.com/fsprojects/FsUnit/releases)
- [Changelog](https://github.com/fsprojects/FsUnit/blob/master/RELEASE_NOTES.md)
- [Commits](https://github.com/fsprojects/FsUnit/commits)

---
updated-dependencies:
- dependency-name: FsUnit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

src/FSharp.Tests/FSharp.Tests.fsproj

@@ -36,7 +36,7 @@
     <ItemGroup>
         <PackageReference Include="NUnit" Version="3.13.2" />
         <PackageReference Include="NUnitLite" Version="3.13.2" />
-        <PackageReference Include="FsUnit" Version="4.0.5" />
+        <PackageReference Include="FsUnit" Version="4.0.6" />
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.10.0" />
         <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.2">
             <PrivateAssets>all</PrivateAssets>