redundant feedback for `I u'

When 3.4.0 added the shop price to inventory display of unpaid items,
it resulted in showing that price twice if you used the `I u' command while
carrying just one unpaid object.

k - a potion of object detection (unpaid, 150 zorkmids)    150 zorkmids

With two or more unpaid objects it uses a menu style display and explicitly
suppresses "(unpaid, N zorkmids)" from the inventory formatting.  Do the
same suppression when there's one item.

k - a potion of object detection                     150 zorkmids

doc/fixes34.4

@@ -108,6 +108,7 @@ fix some cases where movement was disallowed but the hero was still conscious
 after destroying drawbridge, hero could appear to be in the wall
 sometimes shop items which hero is forced to buy could be sold back twice
 vision was not updated when polymorphing a statue into a boulder
+`I u' when carrying single unpaid item listed its cost twice
 
 
 Platform- and/or Interface-Specific Fixes