.background-image-svg-quick() in 'mediawiki.mixins.less has never seemed to get traction.
Even though it follows the DRY principle, I think we should remove centralized code complexity and leave it up to certain projects to have a solution like it implemented themselves.
The original reason (72fc2a68f44a7) to circumvent RL @embed has also been gone for a while now: 792ba935677 (T121730).
SVG fallbacks needs in general should go away anytime soon as well: https://caniuse.com/#feat=svg-css
Proposal
- Deprecate mixin
- Remove mentions of it in codebases we're aware of
- Remove mixin in next version of MediaWiki
Background
Questioning this started in early versions of https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/WikiEditor/+/499881/4/modules/jquery.wikiEditor.dialogs.config.less when thinking about need for the mixin use.
Related task
Removal of background-image-svg() in T248062