build(deps): update Splat.Autofac requirement from 11.* to 12.* in /src (#2855)

Updates the requirements on [Splat.Autofac](https://github.com/reactiveui/splat) to permit the latest version.
- [Release notes](https://github.com/reactiveui/splat/releases)
- [Changelog](https://github.com/reactiveui/splat/blob/main/RELEASENOTES.md)
- [Commits](reactiveui/splat@11.0.1...12.1.1)

---
updated-dependencies:
- dependency-name: Splat.Autofac
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

src/ReactiveUI.Splat.Tests/ReactiveUI.Splat.Tests.csproj

@@ -9,7 +9,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Splat.Autofac" Version="11.*" />
+    <PackageReference Include="Splat.Autofac" Version="12.*" />
     <PackageReference Include="Splat.DryIoc" Version="11.*" />
     <PackageReference Include="Splat.Ninject" Version="12.*" />
   </ItemGroup>