Maintenance: Bump omniauth-facebook from 8.0.0 to 9.0.0

Bumps [omniauth-facebook](https://github.com/simi/omniauth-facebook) from 8.0.0 to 9.0.0.
- [Release notes](https://github.com/simi/omniauth-facebook/releases)
- [Changelog](https://github.com/simi/omniauth-facebook/blob/master/CHANGELOG.md)
- [Commits](https://github.com/simi/omniauth-facebook/compare/v8.0.0...v9.0.0)

Gemfile.lock

@@ -358,7 +358,7 @@ GEM
     omniauth (1.9.1)
       hashie (>= 3.4.6)
       rack (>= 1.6.2, < 3)
-    omniauth-facebook (8.0.0)
+    omniauth-facebook (9.0.0)
       omniauth-oauth2 (~> 1.2)
     omniauth-github (1.4.0)
       omniauth (~> 1.5)