force composer to use 1.x - Update .travis.yml

[joejoseph00]

Composer was recently upgraded to 2.x, composer people upstream are forcing upgrades to 2.x but there's issues with this update, so temporary solution is to force 1.x using the '--1' flag option on composer self update.

see https://www.drupal.org/project/wetkit/issues/3183997#comment-13911763

AND

https://getcomposer.org/doc/03-cli.md

AND

https://github.com/LionsAd/drupal_ti/issues/8

[rikarux]

Thanks @joejoseph00