Update Linked items widget count to use badge instead of icon
Summary
In #474913 (closed) we are adding in the count (by type) for the Child items widget on work items. With that, we are using a badge to indicate the count rather than icons which were used previously in the legacy experience. To keep this treatment consistent, we should follow a similar pattern for the Linked items widget count.
Linked items header (current state)
Proposal
Update the current count in the header of the Linked items widget to use a badge rather than the [Link] icon and text count. The aligns to the treatment of the Child items widget, where the Link icon wasn't providing any real value (and could also be confused with an anchor link).
Although the Child items version includes a popover (with breakout of types as seen here), this is not needed for the Linked items widget at this time. We can consider prioritizing a popover breakout similar to the Child items version but instead by relationship types in the future if we find it is valuable for users.
