chore(deps): update dependency fluentassertions to 8.4.0 (#793)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

src/ReactiveUI.Validation.Tests/ReactiveUI.Validation.Tests.csproj

@@ -24,7 +24,7 @@
     </PackageReference>
     <PackageReference Include="DiffEngine" Version="16.2.2" />
     <PackageReference Include="JetBrains.DotMemoryUnit" Version="3.2.20220510" />
-    <PackageReference Include="FluentAssertions" Version="8.3.0" />
+    <PackageReference Include="FluentAssertions" Version="8.4.0" />
   </ItemGroup>
 
   <ItemGroup>