Travis: don't test incompatible combination OC9.1 + PHP7.1
Travis: don't test incompatible combination OC9.1 + PHP7.1

PHP 7.1 is now the default version for Travis tests, as it should be
compatible at least with all Nextcloud versions. Some ownCloud versions
requrie older or newer PHP which is then set separately.

paulijar/music,paulijar/music,owncloud/music,paulijar/music,paulijar/music,owncloud/music,owncloud/music,paulijar/music,owncloud/music,owncloud/music