Remove workaround for schema.rb

We don't have the schema.rb anymore in the repo, so we don't need it
compatible with both databases anymore.

See 5b1be7d8da

config/application.rb

@@ -10,22 +10,6 @@ require_relative "bundler_helper"
 # you've limited to :test, :development, or :production.
 Bundler.require(*Rails.groups(BundlerHelper.database))
 
-# Do not dump the limit of boolean fields on MySQL,
-# since that generates a db/schema.rb that's incompatible
-# with PostgreSQL
-require 'active_record/connection_adapters/abstract_mysql_adapter'
-module ActiveRecord
-  module ConnectionAdapters
-    class Mysql2Adapter < AbstractMysqlAdapter
-      def prepare_column_options(column, *_)
-        super.tap {|spec|
-          spec.delete(:limit) if column.type == :boolean
-        }
-      end
-    end
-  end
-end
-
 # Load asset_sync early
 require_relative 'asset_sync'