chore(deps): update dependency reactiveui to 20.4.1 (#794)

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

Author: renovate[bot]

src/ReactiveUI.Validation/ReactiveUI.Validation.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="ReactiveUI" Version="20.3.1" />    
+    <PackageReference Include="ReactiveUI" Version="20.4.1" />    
   </ItemGroup>
 
   <ItemGroup Condition="$(TargetFramework.StartsWith('netstandard')) or $(TargetFramework.StartsWith('net4'))">