build(deps): update Autofac requirement from 6.* to 7.* in /src (#999)

Updates the requirements on [Autofac](https://github.com/autofac/Autofac) to permit the latest version.
- [Release notes](https://github.com/autofac/Autofac/releases)
- [Commits](autofac/Autofac@v6.0.0...v7.0.0)

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

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

src/Splat.Autofac/Splat.Autofac.csproj

@@ -9,7 +9,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Autofac" Version="6.*" />
+    <PackageReference Include="Autofac" Version="7.*" />
   </ItemGroup>
 
   <ItemGroup>