fix ka command in kubernetes module (#884)

substring ..-1 not working. Use str trim to remove '-'

modules/kubernetes/mod.nu

@@ -266,7 +266,7 @@ export def --wrapped ka [
     let n = $namespace | with-flag -n
     let pod = if ($selector | is-empty) {
         if ($pod | str ends-with '-') {
-            $"deployment/($pod | str substring ..-1)"
+            $"deployment/($pod | str trim --char '-' --right)"
         } else {
             $pod
         }