ui: [BUGFIX] Add missing `@` to fix missing non-subset Failovers (#10913)

This commit fixes a problem where parent Failovers where not showing (subset children were fine).

Seems to have been introduced with a move/glimmer upgrade here #9154 so I'm adding a 1.9.x backport.

.changelog/10913.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+ui: fixes a bug with some service failovers not showing the routing tab visualization
+```

ui/packages/consul-ui/app/components/consul/discovery-chain/resolver-card/index.hbs

@@ -6,7 +6,7 @@
     onclick={{optional @onclick}} id={{concat 'resolver:' @item.ID}}>
     <a name="">
       <h3>{{@item.Name}}</h3>
-{{#if item.Failover}}
+{{#if @item.Failover}}
       <dl class="failover">
         <dt
           {{tooltip (concat @item.Failover.Type ' failover')}}