(DOCSP-17931): Updated link. (#5815)

* (DOCSP-17931): Updated link.

* Update source/reference/connection-string.txt

Co-authored-by: jdestefano-mongo <[email protected]>

Author: corryroot

source/reference/connection-string.txt

@@ -130,8 +130,8 @@ Examples
            your deployment when you click the :atlas:`Connect
            </connect-to-database-deployment/>` button in the Atlas UI. 
            To register a new Atlas account, start at the 
-           :mdbacct:`MongoDB Atlas registration page 
-           </register?tck=docs_server>`. To learn more, see
+           `MongoDB Atlas registration page 
+           <https://www.mongodb.com/cloud/atlas/register?tck=docs_server_connection_cta>`__. To learn more, see
            :atlas:`Get Started with Atlas </getting-started/>`.
 
            Your Atlas connection string might resemble the following