Fix RAILS_GROUPS and remove rails_12factor

Dockerfile

@@ -27,7 +27,7 @@ ENV RAILS_SERVE_STATIC_FILES=1
 ENV HEROKU=true
 ENV RAILS_ENV=production
 ENV RAILS_CACHE_STORE=memcache
-ENV RAILS_GROUPS="production docker opf_plugins"
+ENV RAILS_GROUPS=production,docker,opf_plugins
 ENV RAILS_LOG_TO_STDOUT=1
 ENV OPENPROJECT_INSTALLATION__TYPE=docker
 # Valid values are: standard,bim

Gemfile

@@ -322,8 +322,7 @@ group :docker, optional: true do
   gem 'passenger', '~> 6.0.1'
 
   # Used to easily precompile assets
-  gem 'newrelic_rpm', '~> 6.9.0.363', require: !!ENV['HEROKU']
-  gem 'rails_12factor', require: !!ENV['HEROKU']
+  gem 'newrelic_rpm', '~> 6.9.0.363'
 end
 
 # Load Gemfile.local, Gemfile.plugins, plugins', and custom Gemfiles