Remove PHP 5.6. and PHP 7.0 jobs from Travis in FirstrunWizard repo for master

[davitol]

As seen in https://travis-ci.org/owncloud/firstrunwizard/builds/359785070?utm_source=github_status&utm_medium=notification PHP 5.6. and PHP 7.0 are no longer supported by oC master branch

[davitol]

@SergioBertolinSG @phil-davis maybe?

[phil-davis]

CI has been moved to drone. drone matrix has the relevant combinations of core master and stable10 with PHP versions.
See issue #85 and PR #86