fix killall background on local network exit

Author: glyh

scripts/mina-local-network/mina-local-network.sh

@@ -4,7 +4,7 @@ set -x
 # Exit script when commands fail
 set -e
 # Kill background process when script exits
-trap "killall background" EXIT
+trap "jobs -p | xargs kill" EXIT
 
 # ================================================
 # Constants