try using out of repo ref and add back legend

Author: lindseymoore

source/compatibility.txt

@@ -27,10 +27,12 @@ The first column lists the version of the library and extension.
 
 .. sharedinclude:: dbx/lifecycle-schedule-callout.rst
 
+.. sharedinclude:: dbx/compatibility-table-legend.rst
+
 .. include:: /includes/mongodb-compatibility-table-php.rst
 
 For more information on how to read the compatibility tables, see our guide on
-`MongoDB Compatibility Tables <https://www.mongodb.com/docs/drivers/about-compatibility/>`__.
+:ref:`MongoDB Compatibility Tables. <about-driver-compatibility>`.
 
 Language Compatibility
 ----------------------