Refine presentation of running pipelines in merge check widget
## Proposal
Change the presentation of the "pipeline must succeed" merge check when currently running.
It is causes confusion if the merge check is still checking or not.

## Initial feedback
From `@stanhu`
> It's a bit confusing. I think the Checking if merge request can be merged should be omitted or rephrased. Perhaps Waiting for all merge request checks...
>
> it implies that it's still checking...
## Potential solutions
1. Would a change to the spinning icon to the pipeline running icon make more sense?
1. I think the icon just really felt like a loading icon, not a “working” icon?
issue