Removed statsd from the api and use the statsd in the utils library.

The statsd code was added to the utils library a while ago, uses the
statsd from the util library and therefore consolidates the code into
once place.

app/celery/tasks.py

@@ -8,6 +8,7 @@ from flask import current_app
 from notifications_utils.recipients import (
     RecipientCSV
 )
+from notifications_utils.statsd_decorators import statsd
 from notifications_utils.template import (
     SMSMessageTemplate,
     WithSubjectTemplate,
@@ -71,7 +72,6 @@ from app.models import (
 )
 from app.notifications.process_notifications import persist_notification
 from app.service.utils import service_allowed_to_send_to
-from app.statsd_decorators import statsd
 from notifications_utils.s3 import s3upload