Added the missin versionadded directive

Author: javiereguiluz

components/browser_kit.rst

@@ -312,6 +312,10 @@ dedicated web crawler or scraper such as `Goutte`_::
         '.table-list-header-toggle a:nth-child(1)'
     )->text());
 
+.. versionadded:: 4.3
+
+    The feature to make external HTTP requests was introduced in Symfony 4.3.
+
 Learn more
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