fix typo in test runner link (SeleniumHQ#2193)

There was a typo in the link to the Test Runner section in the
Documentation > WebDriver > Getting Started > Using Selenium page.
The link is found under the 'Common Uses' headline and 'Testing'
subheadline.

Co-authored-by: Sri Harsha <12621691+harsha509@users.noreply.github.com>

Author: franciscotrenco

website_and_docs/content/documentation/webdriver/getting_started/using_selenium.en.md

@@ -34,7 +34,7 @@ terms of service as some websites do not permit it and others will even block Se
 
 Running Selenium for testing requires making assertions on actions taken by Selenium.
 So a good assertion library is required. Additional features to provide structure for tests
-require use of [Test Runner](#test-runners).
+require use of [Test Runner](#test-runner).
 
 ## IDEs