Fix RST syntax

Author: javiereguiluz

notifier.rst

@@ -50,7 +50,7 @@ a third-party service that sends SMS messages. Symfony provides integration
 with a couple popular SMS services:
 
 ========  =============================  ===========================================
-Service  Package                         DSN
+Service   Package                        DSN
 ========  =============================  ===========================================
 Twilio    ``symfony/twilio-notifier``    ``twilio://SID:TOKEN@default?from=FROM``
 Nexmo     ``symfony/nexmo-notifier``     ``nexmo://KEY:SECRET@default?from=FROM``