Bump Selenium.WebDriver from 4.20.0 to 4.21.0 in /src

Bumps [Selenium.WebDriver](https://github.com/SeleniumHQ/selenium) from 4.20.0 to 4.21.0.
- [Release notes](https://github.com/SeleniumHQ/selenium/releases)
- [Commits](SeleniumHQ/selenium@selenium-4.20.0...selenium-4.21.0)

---
updated-dependencies:
- dependency-name: Selenium.WebDriver
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

src/IoTHub.Portal.Tests.E2E/IoTHub.Portal.Tests.E2E.csproj

@@ -33,7 +33,7 @@
     <PackageReference Include="NUnit.Analyzers" Version="3.10.0" />
     <PackageReference Include="coverlet.collector" Version="6.0.2" />
     <PackageReference Include="Selenium.Support" Version="4.20.0" />
-    <PackageReference Include="Selenium.WebDriver" Version="4.20.0" />
+    <PackageReference Include="Selenium.WebDriver" Version="4.21.0" />
     <PackageReference Include="Selenium.WebDriver.ChromeDriver" Version="118.0.5993.7000" />
   </ItemGroup>