chore: update interpolation syntax for i18n files (#10198)

There were two warnings showing up on new teams page

1. `errorMessage` prop was getting invalid value, this was because were
short circuting the error message using `&&`, fixed it by using ternary
operator
2. `vue-i18n` has deprecated [rails
syntax](https://vue-i18n.intlify.dev/guide/essentials/syntax#rails-i18n-format),
fixed that warning by removing `%` before `{}` for interpolation

> Note: the `vue-i18n` deprecation needs to be handled, but we can do it
later

app/javascript/dashboard/i18n/locale/is/bulkActions.json

@@ -1,9 +1,9 @@
 {
   "BULK_ACTION": {
-    "CONVERSATIONS_SELECTED": "%{conversationCount} samtöl valin",
+    "CONVERSATIONS_SELECTED": "{conversationCount} samtöl valin",
     "AGENT_SELECT_LABEL": "Velja þjónustufulltrúa",
-    "ASSIGN_CONFIRMATION_LABEL": "Ertu viss um að úthluta %{conversationCount} %{conversationLabel} á",
-    "UNASSIGN_CONFIRMATION_LABEL": "Ertu viss um að hætta við úthlutun %{conversationCount} %{conversationLabel}?",
+    "ASSIGN_CONFIRMATION_LABEL": "Ertu viss um að úthluta {conversationCount} {conversationLabel} á",
+    "UNASSIGN_CONFIRMATION_LABEL": "Ertu viss um að hætta við úthlutun {conversationCount} {conversationLabel}?",
     "GO_BACK_LABEL": "Go back",
     "ASSIGN_LABEL": "Úthluta",
     "YES": "Já",