Bump Verify.NUnit from 20.7.0 to 20.8.0 in /src (#460)

Bumps [Verify.NUnit](https://github.com/VerifyTests/Verify) from 20.7.0 to 20.8.0.
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](VerifyTests/Verify@20.7.0...20.8.0)

---
updated-dependencies:
- dependency-name: Verify.NUnit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

src/Tests/Tests.csproj

@@ -10,7 +10,7 @@
     <PackageReference Include="NUnit" Version="3.13.3" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.0" />
-    <PackageReference Include="Verify.NUnit" Version="20.7.0" />
+    <PackageReference Include="Verify.NUnit" Version="20.8.0" />
     <PackageReference Include="Verify.DiffPlex" Version="2.2.1" />
     <PackageReference Include="ProjectDefaults" Version="1.0.91" PrivateAssets="all" />
     <ProjectReference Include="..\AssemblyToProcess\AssemblyToProcess.csproj" />