Remove secrets from config/environment.rb

Code already depends on this information being set as an environment
variable anyway.

Change-Id: Ia5aee2b344548128af8107870d57d76f96bd2705
Reviewed-on: https://gerrit.causes.com/22711
Tested-by: Aiden Scandella <aiden@causes.com>
Reviewed-by: Greg Hurrell <greg@causes.com>