chore(deps): update dependency verify.xunit to v28

Author: renovate[bot]

Diff for: src/directory.packages.props

@@ -33,7 +33,7 @@
   <ItemGroup>
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageVersion Include="Verify.SourceGenerators" Version="1.3.0" />
-    <PackageVersion Include="Verify.Xunit" Version="14.14.1" />
+    <PackageVersion Include="Verify.Xunit" Version="28.7.1" />
     <PackageVersion Include="ReactiveMarbles.SourceGenerator.TestNuGetHelper" Version="1.3.1" />
   </ItemGroup>