Import request cache from utils

We’ve making the request cache shared code now so we can remove it from
this app and refer to the version in utils instead.

Delete unused module

app/notify_client/__init__.py

@@ -2,6 +2,11 @@ from flask import abort, has_request_context, request
 from flask_login import current_user
 from notifications_python_client import __version__
 from notifications_python_client.base import BaseAPIClient
+from notifications_utils.clients.redis import RequestCache
+
+from app.extensions import redis_client
+
+cache = RequestCache(redis_client)
 
 
 def _attach_current_user(data):