Help icons popovers on epics issuable sidebar do not summon on hover

Problem

Help icons popovers on epics issuable sidebar do not summon on hover and thus now follow https://design.gitlab.com/components/popovers

Solution

As per https://design.gitlab.com/components/popovers

Popovers fade in upon hover or touch of its trigger element. They fade out upon interacting with an area or element outside of the popover or its trigger, or on a delay of the cursor moving outside the popover or its trigger element.

Popovers should be summoned on hover or touch

cc: @pedroms @victorwu @annabeldunstone