doc: fix TestsStream parent class

PR-URL: #51181
Fixes: #51174
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

Author: Jungku Lee

doc/api/test.md

@@ -2420,7 +2420,7 @@ changes:
     description: added type to test:pass and test:fail events for when the test is a suite.
 -->
 
-* Extends {ReadableStream}
+* Extends {Readable}
 
 A successful call to [`run()`][] method will return a new {TestsStream}
 object, streaming a series of events representing the execution of the tests.