chore(deps): update dependency system.collections.immutable to 9.0.4

Author: renovate[bot]

src/ReactiveUI.Validation/ReactiveUI.Validation.csproj

@@ -12,6 +12,6 @@
   </ItemGroup>
 
   <ItemGroup Condition="$(TargetFramework.StartsWith('netstandard')) or $(TargetFramework.StartsWith('net4'))">
-    <PackageReference Include="System.Collections.Immutable" Version="9.0.3" />
+    <PackageReference Include="System.Collections.Immutable" Version="9.0.4" />
   </ItemGroup>
 </Project>