fix typo for welcome osf4i email

Author: Johnetordoff

notifications.yaml

@@ -44,7 +44,7 @@ notification_types:
     object_content_type_model_name: osfuser
     template: 'website/templates/emails/forgot_password.html.mako'
     notification_freq_default: instantly
-  - name: welcome_osf4i
+  - name: user_welcome_osf4i
     __docs__: ...
     object_content_type_model_name: osfuser
     template: 'website/templates/emails/welcome_osf4i.html.mako'