Update Verify to 28.5.0 (#3845)

Author: SimonCropp

test/Directory.Build.props

@@ -56,7 +56,7 @@
 
   <!-- only non-platform-specific projects should include these packages -->
   <ItemGroup Condition="'$(TargetPlatformIdentifier)'==''">
-    <PackageReference Include="Verify.Xunit" Version="26.6.0" />
+    <PackageReference Include="Verify.Xunit" Version="28.5.0" />
     <PackageReference Include="Verify.DiffPlex" Version="2.3.0" />
     <PackageReference Include="PublicApiGenerator" Version="11.1.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" PrivateAssets="All" />