Fix cluster's badge position

[momesgin]

Summary

Fixes #10667

A 4-pixel transparent border was affecting the positioning of the colored border. I could not figure out why this transparent border was added in the first place, but tried to test this change manually as much as I could in order to prevent any visual regression.

Areas or cases that should be tested

The cluster badge should be displayed properly in different states(e.g. active, disabled) and for different cluster types(e.g. local, custom)

Areas which could experience regressions

Same as above.

Screenshot/Video

Checklist

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[momesgin]

@scures I was wondering if you would know what that transparent border is used for?

[scures]

Before it was an actual border (border-bottom) and I had to add a transparent one so the elements were of the same height (font+4px border)
But later, I changed that; there's now an element instead of a border

It's safe to remove it. Thanks for spotting it =)