Steps to replicate the issue (include links if applicable):

• Load https://www.wikidata.org/wiki/Lexeme:L7
• Use the browser dev tools to inspect the edit icon for the lemmas

What happens?:

The CSS for .wb-lexeme .lemma-widget_edit:before has two background-image rules, both of which are PNGs.

What should have happened instead?:

The second CSS rule should be an SVG.

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

The CSS for editing lemmas: https://github.com/wikimedia/mediawiki-extensions-WikibaseLexeme/blob/master/resources/lemma-widget.less#L48

The CSS used elsewhere: https://github.com/wikimedia/Wikibase/blob/master/view/resources/jquery/wikibase/toolbar/themes/default/jquery.wikibase.toolbarbutton.css#L66