DOCSP-49301 Fix X.509 MongoCredential code example (#590) (#597)

(cherry picked from commit be38a20)

Co-authored-by: Stephanie <[email protected]>

Author: github-actions[bot]

source/fundamentals/authentication/x509.txt

@@ -38,10 +38,12 @@ Code Placeholders
 
 The code examples on this page use the following placeholders:
 
-- ``+srv``: Include this option in your connection string prefix only if you are connecting
-  to a MongoDB Atlas cluster. To learn more about the ``+srv`` option, see
-  :manual:`Connection String Formats </reference/connection-string/#connection-string-formats>`
-  in the {+mdb-server+} manual.
+- ``+srv``: Include this option in your connection string prefix only if you are
+  connecting to a MongoDB Atlas cluster. If you're using a
+  ``MongoClientSettings`` object, you can specify the ``srv`` format by setting
+  the ``Scheme`` property to ``ConnectionStringScheme.MongoDBPlusSrv``. To learn
+  more about the ``+srv`` option, see :manual:`Connection String Formats </reference/connection-string/#connection-string-formats>` in the
+  {+mdb-server+} manual.
 - ``<hostname>``: The network address of your MongoDB deployment.
 - ``<port>``: The port number of the MongoDB deployment. If you omit this parameter,
   the driver uses the default port number (``27017``). You don't need a port number
@@ -119,6 +121,7 @@ see the corresponding syntax:
              },
              UseTls = true,
              Server = new MongoServerAddress("<hostname>"[, "<port>"]),
+             Scheme = ConnectionStringScheme.MongoDBPlusSrv, // Needed when connecting to MongoDB Atlas
          };
 
 Troubleshooting