Remove Mongo initializer
Remove Mongo initializer

It duplicates SlackBotServer::Api#silence_loggers!

dblock/slack-bot-server,dblock/slack-bot-server,slack-ruby/slack-ruby-bot-server,dblock/slack-bot-server,dblock/slack-ruby-bot-server,dblock/slack-bot-server,slack-ruby/slack-ruby-bot-server,slack-ruby/slack-ruby-bot-server,dblock/slack-ruby-bot-server,dblock/slack-ruby-bot-server