Revert "DOCSP-48720 Update non-MongoDB credentials (#150)"

This reverts commit f47c1a5.

Author: lindseymoore

source/security/auth-mechanisms/scram.txt

@@ -49,8 +49,8 @@ The code examples on this page use the following placeholders:
   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.
-- ``<db_username>``: The MongoDB username of the user to authenticate.
-- ``<db_password>``: The MongoDB password of the user to authenticate.
+- ``<username>``: The MongoDB username of the user to authenticate.
+- ``<password>``: The MongoDB password of the user to authenticate.
 - ``<hostname>``: The network address of your MongoDB deployment.
 - ``<port>``: The port number of your MongoDB deployment. If you omit this parameter,
   the driver uses the default port number (``27017``). You don't need a port number
@@ -78,16 +78,16 @@ see the corresponding syntax:
 
       .. code-block:: ruby
 
-         client = Mongo::Client.new('mongodb[+srv]://<db_username>:<db_password>@<hostname>[:<port>]/?authSource=<authentication_db>')
+         client = Mongo::Client.new('mongodb[+srv]://<username>:<password>@<hostname>[:<port>]/?authSource=<authentication_db>')
 
    .. tab:: Client Options
       :tabid: default-mongo-credential
 
       .. code-block:: ruby
 
          client = Mongo::Client.new('<hostname>',
-                                    user: '<db_username>',
-                                    password: '<db_password>')
+                                    user: '<username>',
+                                    password: '<password>')
 
 API Documentation
 -----------------