trivial: duplicate atlas target name

Author: kay-kim

source/tutorial/atlas-free-tier-setup.txt

@@ -9,7 +9,7 @@ Create an Atlas Free Tier Cluster
 .. default-domain:: mongodb
 
 `MongoDB Atlas
-<https://www.mongodb.com/cloud/atlas?utm_source=atlas-free-tier-setup&utm_campaign=20-docs-in-20-days&utm_medium=docs>`_
+<https://www.mongodb.com/cloud/atlas?utm_source=atlas-free-tier-setup&utm_campaign=20-docs-in-20-days&utm_medium=docs>`__
 is a cloud-hosted service for provisioning, running, monitoring, and
 maintaining MongoDB deployments. It is a fast, easy, and free way to get
 started with MongoDB. To install and run MongoDB locally, see :ref:`Install