Fix extra border on custom stage form groups

What does this MR do?

Fixes a minor extra border that was appearing around form group elements. The form-group needs an extra label-for attribute to render the group with a div and label instead of the default fieldset and legend.

No changelog added since this is still behind the :customizable_cycle_analytics feature flag

Fixes #207966 (closed)

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Closes #207966 (closed)