Fix ActiveRecord::Relation#touch_all with custom attribute aliased as attribute for update

[fatkodima]

If we have something like

create_table :users do |t|
  t.timestamp :legacy_updated_at
end

class User < ActiveRecord::Base
  alias_attribute :updated_at, :legacy_updated_at
end

User.touch_all(:updated_at)

then ActiveRecord will not resolve updated_at to its alias correctly and result to a query that updates the same column twice.

For PostgreSQL, this produces an error similar to this:

ActiveRecord::StatementInvalid: PG::SyntaxError: ERROR:  multiple assignments to same column "legacy_updated_at"