Update dependency FluentAssertions to v6

Author: renovate[bot]

tests/Tests.csproj

@@ -15,7 +15,7 @@
     <PackageReference Include="AWSSDK.S3" Version="3.7.1" />
     <PackageReference Include="AutoFixture.NUnit3" Version="4.17.0" />
     <PackageReference Include="coverlet.collector" Version="3.1.0" PrivateAssets="all" />
-    <PackageReference Include="FluentAssertions" Version="5.10.3" />
+    <PackageReference Include="FluentAssertions" Version="6.12.0" />
     <PackageReference Include="Microsoft.Build.Locator" Version="1.5.5" />
     <PackageReference Include="Microsoft.CodeAnalysis.Workspaces.MSBuild" Version="4.5.0" />
     <PackageReference Include="NSubstitute" Version="4.2.2" />