Wikibase (among it's toolbar labelled source) currently features outdated icons back from before T177432
Let's standardize gently.
While the old canvas was 20x20px the icons themselves took up an inconsistently smaller amount of space. That was a.o. one of the reasons for T117432.
Some of those in action:
 Update icons (all from OOUI before T177432) to latest
[x] Update pre-OOUI help icon to be replaced by 'helpNotice' icon – https://gerrit.wikimedia.org/r/483124
 Amend `background-size` so the icon size remains about the same (~16 x 16 px)
 Follow icon `opacity` rule on active elements from [[ https://phabricator.wikimedia.org/diffusion/WMUI/ | WikimediaUI Base ]] and OOUI.
* [[ https://doc.wikimedia.org/oojs-ui/master/demos/?page=icons&theme=wikimediaui&direction=ltr&platform=desktop | OOUI icons ]]
* [[ https://design.wikimedia.org/style-guide/visual-style_icons.html | Wikimedia Design Style Guide – Icon design and sizes ]]