Bump Verify.Xunit from 26.3.1 to 26.4.2 in /src

Bumps [Verify.Xunit](https://github.com/VerifyTests/Verify) from 26.3.1 to 26.4.2.
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](VerifyTests/Verify@26.3.1...26.4.2)

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

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

src/Fluss.UnitTest/Fluss.UnitTest.csproj

@@ -15,7 +15,7 @@
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.0" />
         <PackageReference Include="Moq" Version="4.20.70" />
         <PackageReference Include="Verify.SourceGenerators" Version="2.4.0"/>
-        <PackageReference Include="Verify.Xunit" Version="26.3.1"/>
+        <PackageReference Include="Verify.Xunit" Version="26.4.2"/>
         <PackageReference Include="xunit" Version="2.9.0"/>
         <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>