Polish the Y-Axis of the Insights charts

As noted here: https://gitlab.com/gitlab-org/quality/team-tasks/issues/129#note_177343080

Another observation from me, is there a reason to have decimal numbers in the y axis for issue counts?

The chart shows only 1 issue. I was expecting the y axis to be 1,2,3,4,5,6,7,8 and the bar shorter. We may need to look into default graph value/height ?

We should improve that.