Adjust resting positions for SMS providers

It's worth noting this will break the Admin page to edit provider
priorities, which currently works in units of 10. We already have
work planned to fix this [^1] and it's not an immediate problem.

The automatic adjustment algorithm will continue to work properly
as it can cope with increments smaller than 10 [^2].

[^1]: https://www.pivotaltracker.com/story/show/181681739
[^2]: https://github.com/alphagov/notifications-api/blob/b145a299351255c5755ca547629b7936cb7fcf4a/app/dao/provider_details_dao.py#L122

app/config.py

@@ -161,8 +161,8 @@ class Config(object):
 
     # these should always add up to 100%
     SMS_PROVIDER_RESTING_POINTS = {
-        'mmg': 50,
-        'firetext': 50
+        'mmg': 55,
+        'firetext': 45
     }
 
     NOTIFY_SERVICE_ID = 'd6aa2c68-a2d9-4437-ab19-3ae8eb202553'