MONGOID-5250 Replace connect: :direct with direct_connection: true in documentation (#5157)

* MONGOID-5250 update docs to refer to direct_connection

* MONGOID-5250 get rid of back ticks

Author: neilshweky

source/reference/configuration.txt

@@ -185,9 +185,17 @@ for details on driver options.
 
           # Force the driver to connect in a specific way instead of auto-
           # discovering. Can be one of: :direct, :replica_set, :sharded. Set to :direct
-          # when connecting to hidden members of a replica set.
+          # when connecting to hidden members of a replica set. This option is deprecated
+          # and using it to specify :replica_set or :sharded is generally unnecessary.
+          # To force the client to use a direct connection, it is recommended that the
+          # direct_connection option be used.
           connect: :direct
 
+          # To disable the deployment type discovery and force all operations to be
+          # performed on a particular server, specify the direct_connection option
+          # as true. (default: false)
+          direct_connection: false
+
           # Change the default time in seconds the server monitors refresh their status
           # via hello commands. (default: 10)
           heartbeat_frequency: 10