[Fix] Popover: add border to arrow

[edschema]

The popover arrow border is lighter than the border for the rest of the popover.

Desired behavior
Set the popover arrow color to match the rest of the popover border.

Fix shape
in popover.json, line 22 where the arrow border is defined, remove

"modify": [{ "type": "alpha", "amount": 0.05 }],

the source token color.popover.border already has 20% alpha applied, so the modify is further reducing opacity making it render much lighter than the rest of the border