remove loadtesting from providers

we don't use it since we wrote our own provider stubs for performance
tests.

this removes it from the api - it's still in the DB and will be
retrieved by queries, but is set to disabled on prod

app/clients/sms/loadtesting.py

@@ -1,24 +0,0 @@
-import logging
-
-from flask import current_app
-
-from app.clients.sms.firetext import (
-    FiretextClient
-)
-
-logger = logging.getLogger(__name__)
-
-
-class LoadtestingClient(FiretextClient):
-    '''
-    Loadtest sms client.
-    '''
-
-    def init_app(self, config, statsd_client, *args, **kwargs):
-        super(FiretextClient, self).__init__(*args, **kwargs)
-        self.current_app = current_app
-        self.api_key = config.config.get('LOADTESTING_API_KEY')
-        self.from_number = config.config.get('FROM_NUMBER')
-        self.name = 'loadtesting'
-        self.url = "https://www.firetext.co.uk/api/sendsms/json"
-        self.statsd_client = statsd_client