returners/sentry_return.py: fix indents & spacing

This was caught by Travis! https://travis-ci.org/saltstack/salt/jobs/9017807
```
************* Module salt.returners.sentry_return
W0311: 66,0: Bad indentation. Found 11 spaces, expected 12
W0311: 67,0: Bad indentation. Found 15 spaces, expected 16
W0311: 70,0: Bad indentation. Found 11 spaces, expected 12
C0322: 70,11:returner.connect_sentry: Operator not preceded by a space
           data['level']='info'
```