Remove redundant stage settings

These files are only loaded when the stage already has the value set
inside them, so we don't need to set it again.

On the other hand, the `rails_env` setting is configured in the
`config/deploy.rb` file.

config/deploy/preproduction.rb

@@ -3,8 +3,6 @@ set :server_name, deploysecret(:server_name)
 set :db_server, deploysecret(:db_server)
 set :branch, ENV["branch"] || :master
 set :ssh_options, port: deploysecret(:ssh_port)
-set :stage, :preproduction
-set :rails_env, :preproduction
 
 server deploysecret(:server1), user: deploysecret(:user), roles: %w[web app db importer cron background]
 server deploysecret(:server2), user: deploysecret(:user), roles: %w[web app db importer]

config/deploy/production.rb

@@ -3,8 +3,6 @@ set :server_name, deploysecret(:server_name)
 set :db_server, deploysecret(:db_server)
 set :branch, :master
 set :ssh_options, port: deploysecret(:ssh_port)
-set :stage, :production
-set :rails_env, :production
 
 server deploysecret(:server1), user: deploysecret(:user), roles: %w[web app db importer cron background]
 #server deploysecret(:server2), user: deploysecret(:user), roles: %w(web app db importer cron background)

config/deploy/staging.rb

@@ -3,7 +3,5 @@ set :server_name, deploysecret(:server_name)
 set :db_server, deploysecret(:db_server)
 set :branch, ENV["branch"] || :master
 set :ssh_options, port: deploysecret(:ssh_port)
-set :stage, :staging
-set :rails_env, :staging
 
 server deploysecret(:server), user: deploysecret(:user), roles: %w[web app db importer cron]