Edit critical to be Important to align with the rest of app convention (#2063)

# What this PR does
- Edits the send important notification button to be send critical
notification button to align with the app conventions
## Which issue(s) this PR fixes
Ref #2043

grafana-plugin/src/containers/MobileAppConnection/MobileAppConnection.tsx

@@ -215,7 +215,7 @@ const MobileAppConnection = observer(({ userPk }: Props) => {
                 onClick={() => onSendTestNotification(true)}
                 disabled={isAttemptingTestNotification}
               >
-                Send Critical Test Push notification
+                Send Important Test Push notification
               </Button>
             </HorizontalGroup>
           </div>