Kill with -9 flag

Summary: There are reports in which kill as is doesn't kill the process. Using the '-9' flag does, so update troubleshoot message.

Reviewed By: LukeDefeo

Differential Revision: D49537427

fbshipit-source-id: a062c92528589cecf0f41e1c344c5d0ae1c3345d

desktop/flipper-ui-core/src/dispatcher/flipperServer.tsx

@@ -210,7 +210,7 @@ function handeEADDRINUSE(errorMessage: string) {
         <br />
         <br />
         Please try to kill the offending process by running{' '}
-        <code>sudo kill $(lsof -ti:PORTNUMBER)</code> and restart flipper.
+        <code>sudo kill -9 $(lsof -ti:PORTNUMBER)</code> and restart flipper.
         <br />
         <br />
         {errorMessage}