Update Splat requirement from 7.* to 8.* (#49)

Updates the requirements on [Splat](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/master/RELEASENOTES.md)
- [Commits](reactiveui/splat@7.0.1...8.0.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

src/Fusillade/Fusillade.csproj

@@ -6,7 +6,7 @@
 
   <ItemGroup>
     <PackageReference Include="punchclock" Version="3.*" />
-    <PackageReference Include="Splat" Version="7.*" />
+    <PackageReference Include="Splat" Version="8.*" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
     <PackageReference Include="System.Reactive" Version="4.1.5" />
   </ItemGroup>