Bump raven from 6.9.0 to 6.10.0 (#1478)

Bumps [raven](https://github.com/getsentry/raven-python) from 6.9.0 to 6.10.0.
- [Release notes](https://github.com/getsentry/raven-python/releases)
- [Changelog](https://github.com/getsentry/raven-python/blob/master/CHANGELOG.md)
- [Commits](getsentry/raven-python@6.9.0...6.10.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

prod-requirements.txt

@@ -1,6 +1,6 @@
 gunicorn==19.9.0
 
-raven==6.9.0
+raven==6.10.0
 
 # Heroku
 Whitenoise