Bump Verify.Nunit and Microsoft.NETFramework.ReferenceAssemblies in /src

Bumps [Verify.Nunit](https://github.com/VerifyTests/Verify) and [Microsoft.NETFramework.ReferenceAssemblies](https://github.com/Microsoft/dotnet). These dependencies needed to be updated together.

Updates `Verify.Nunit` from 28.7.1 to 28.8.1
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](https://github.com/VerifyTests/Verify/commits)

Updates `Microsoft.NETFramework.ReferenceAssemblies` from 1.0.3 to 1.0.3
- [Commits](https://github.com/Microsoft/dotnet/commits)

---
updated-dependencies:
- dependency-name: Verify.Nunit
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: Microsoft.NETFramework.ReferenceAssemblies
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

src/Directory.Packages.props

@@ -17,7 +17,7 @@
     <PackageVersion Include="ProjectDefaults" Version="1.0.144" />
     <PackageVersion Include="PropertyChanged.Fody" Version="4.1.0" />
     <PackageVersion Include="System.Runtime.InteropServices.RuntimeInformation" Version="4.3.0" />
-    <PackageVersion Include="Verify.NUnit" Version="28.7.1" />
+    <PackageVersion Include="Verify.NUnit" Version="28.8.1" />
     <PackageVersion Include="Xamarin.Essentials" Version="1.8.0" />
     <PackageVersion Include="Xamarin.Google.Android.Material" Version="1.10.0.1" />
   </ItemGroup>