Remove ruby version constraint from Gemfile
Remove ruby version constraint from Gemfile

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