DOCSP-31209 Add warning about QE with Atlas (#3903)

* add warning about QE with Atlas

* Mike feedback

* source constant

* Cynthia feedback

Author: jordan-smith721

source/core/queryable-encryption/install.txt

@@ -35,6 +35,11 @@ in your development environment:
   or a
   :manual:`MongoDB Enterprise instance
   </tutorial/manage-mongodb-processes/#start-mongod-processes>`
+
+  .. warning::
+
+     You can use {+qe+} only with MongoDB 7.0 and later, which
+     may not yet be available in MongoDB Atlas.
 
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