chore(deps): update dependency reactiveui to v19.6.12 (#78)

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

Author: renovate[bot]

src/ReactiveMvvm/ReactiveMvvm.csproj

@@ -4,6 +4,6 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="ReactiveUI.Fody" Version="19.5.41" />
-    <PackageReference Include="ReactiveUI" Version="19.6.1" />
+    <PackageReference Include="ReactiveUI" Version="19.6.12" />
   </ItemGroup>
 </Project>