Teach scripts/db_tasks to know about database_tasks:false

This script attempts to append :main if there's only one DB effectively.
To make this work in the case where we have two connections to main, we
need to reject ci config where database_tasks: false.

scripts/db_tasks

@@ -5,6 +5,7 @@ require 'yaml'
 
 rails_env = ENV.fetch('RAILS_ENV')
 database_config = YAML.load_file(File.join(File.expand_path('..', __dir__), 'config', 'database.yml'))[rails_env]
+database_config.reject! { |_k, v| v["database_tasks"] == false }
 
 task = ARGV.shift
 raise ArgumentError, 'You need to pass a task name!' unless task