hive ui: remove the counters on the tabs

The pills on 4G3NTS, R3BU1LD QU3U3 and K3PT ST4T3, the poll that fed them, the
two count helpers, their styles, and the tab strip's unused badge option.

frontend/packages/dashboard/src/kept.js

@@ -23,11 +23,6 @@ const fmtAgeDays = (ts) => {
   return d + " days ago";
 };
 
-/** Number of kept-state entries, for the tab's count pill. */
-export function keptCount() {
-  return tombstonesState.length;
-}
-
 export function syncKeptFromSnapshot(s) {
   tombstonesState = (s.tombstones || []).slice();
 }