Hardcode database pool size for sidekiq

For some reason pool is set to 1 and I can't find the source of this
setting, so for now, just to fix the immediate problem I'm setting it
manually in sidekiq.rb

lib/travis/sidekiq.rb

@@ -7,6 +7,7 @@ require 'travis/api/workers/job_cancellation'
 require 'travis/api/workers/job_restart'
 require 'travis/support/amqp'
 
+Travis.config.database[:pool] = 5
 Travis::Database.connect
 
 if Travis.config.logs_database