Legend/popover colour chip update for bar chart
## Problem From discussion here: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/issues/614#note_364661865 - The color chip in the legend/popover doesn't really match the columns in charts - It's hard to recognise that you can actually click chips in the legend to show/hide values in chart - It's current hard to differentiate between lines and columns on the same chart: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/issues/615 ## Solution Legend/popover colour chip update for bar chart Style as described here: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/issues/617#note_370810027
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