Bump Argon and Verify.Xunit in /src (#586)

Bumps [Argon](https://github.com/SimonCropp/Argon) and [Verify.Xunit](https://github.com/VerifyTests/Verify). These dependencies needed to be updated together.

Updates `Argon` from 0.26.0 to 0.26.0
- [Release notes](https://github.com/SimonCropp/Argon/releases)
- [Commits](SimonCropp/Argon@0.26.0...0.26.0)

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

---
updated-dependencies:
- dependency-name: Argon
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: Verify.Xunit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

src/Directory.Packages.props

@@ -25,7 +25,7 @@
     <PackageVersion Include="Verify.DiffPlex" Version="3.1.2" />
     <PackageVersion Include="Verify.ImageMagick" Version="3.6.0" />
     <PackageVersion Include="Verify.WinForms" Version="4.0.0" />
-    <PackageVersion Include="Verify.Xunit" Version="28.7.1" />
+    <PackageVersion Include="Verify.Xunit" Version="28.8.1" />
     <PackageVersion Include="Xunit" Version="2.9.2" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="3.0.0" />
     <PackageVersion Include="XunitContext" Version="3.3.2" />