chore(deps): update dependency splat to v21 (#402)

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

Author: renovate[bot]

src/Directory.Packages.props

@@ -18,7 +18,7 @@
     <PackageVersion Include="ReactiveUI.Primitives.Reactive" Version="7.1.0" />
     <PackageVersion Include="ReactiveUI.Primitives.Blazor" Version="7.1.0" />
     <PackageVersion Include="ReactiveUI.Primitives.Blazor.Reactive" Version="7.1.0" />
-    <PackageVersion Include="Splat" Version="20.2.0" />
+    <PackageVersion Include="Splat" Version="21.0.0" />
     <PackageVersion Include="PublicApiGenerator" Version="11.5.4" />
     <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="10.0.301" />
     <PackageVersion Include="MinVer" Version="7.0.0" />