For context, the 'help' icon change from circled to non-circled in the general icon unification and refinement task T177432, which aimed at the help icons usage in toolbars and was a last-minute change to get it through. It was rightfully criticized in T191014#4229540 in places other than toolbars. Now we're providing two icons, 'helpNotice' should improve the experience in cases like RevisionSlider.
The icon was in a circle before, see https://commons.wikimedia.org/wiki/File:Revisionslider-screenshot-de-large.png. So the fact it became a stray "?" is technically a regression, and the patch technically a bugfix. I went ahead and merged it. Can easily be rolled back in case WMDE-Design doesn't agree.