Always use LFS when running UI tests

[tsteur]

Currently, when we are wanting to use LFS in a Matomo plugin which is in its own submodule/github repo then we need to do the following steps as documented in https://developer.matomo.org/guides/maintaining-plugins#how-do-i-fix-the-error-some-screenshots-are-not-stored-in-lfs to get travis to use LFS.

Ideally, this would not be needed and we'd simply always use LFS in the default travis already. This will simplify things for when we have new plugins.

Once we added it to the default travis yml then we should remove the documented part from the link above.

[sgiehl]

Guess the most "correct" solution would be to do this for all generated travis files:

travis-scripts/generator/templates/travis.yml.twig

Lines 111 to 113 in 17d2296

	{% if generationMode == 'core' %}
	- . ./tests/travis/install_git_lfs.sh
	{% endif %}

But that will require updating all travis.yml files

[tsteur]

👍 I suppose we don't need to do it for now as we rarely add new plugins now but eventually it be great to do it when we maybe have some other change for travis yml that requires updating them

[sgiehl]

That should also work with the new github action tests