Bump Microsoft.NET.Test.Sdk from 18.3.0 to 18.4.0

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-version: 18.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

test/Html2Markdown.Test/Html2Markdown.Test.csproj

@@ -7,7 +7,7 @@
     <ItemGroup>
         <PackageReference Include="FluentAssertions" Version="8.0.0-alpha.1"/>
         <PackageReference Include="JunitXml.TestLogger" Version="8.0.0"/>
-        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.3.0"/>
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.4.0"/>
         <PackageReference Include="Verify.Xunit" Version="31.12.5"/>
         <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
             <PrivateAssets>all</PrivateAssets>