Fix unit display for VSA charts

What does this MR do and why?

Fixes the display of small units in VSA charts. Ensures that decimals are not converted to engineering notation, instead the formatter will just pass the

This is related to Provide options to configure displayed units in... (gitlab-ui#580) and has occurred in a few other parts of analytics.

Screenshots or screen recordings

Before - 500M	After - 0.5

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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Related to #351686 (closed)