fix(css): remove desktop-first CSS utils

BREAKING CHANGE: This removes the remaining desktop-first CSS utilities
form the library. Any usages of those should be replaced with
mobile-first alternatives. See below for replacement suggestions. Note
that the proposed replacements should work in the most simple cases.
Some use cases might require using different utils combinations.

* `gl-sm-flex-direction-column`
Replace with `gl-flex-direction-column gl-md-flex-direction-row`.

* `gl-xs-flex-direction-column`
Replace with `gl-flex-direction-column gl-sm-flex-direction-row`.

* `gl-xs-w-full`
Replace with `gl-w-full gl-sm-w-auto`.

* `gl-xs-mb-3`
Replace with `gl-mb-3 gl-sm-mb-0`.