minor #15258 remove 4.x versionadded directive (xabbuh)

This PR was merged into the 5.2 branch.

Discussion
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remove 4.x versionadded directive

Commits
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3857676 remove 4.x versionadded directive

Author: xabbuh

testing.rst

@@ -843,12 +843,6 @@ useful test assertions::
     // ...or check that the response is a redirect to any URL
     $this->assertResponseRedirects();
 
-.. versionadded:: 4.3
-
-    The ``assertResponseHeaderSame()``, ``assertResponseIsSuccessful()``,
-    ``assertResponseStatusCodeSame()``, ``assertResponseRedirects()`` and other
-    related methods were introduced in Symfony 4.3.
-
 .. index::
    single: Tests; Crawler