use testnet policy config

Author: ma2bd

backend/README.md

@@ -22,7 +22,7 @@ Start the local Linera network and run a faucet:
 ```bash
 FAUCET_PORT=8079
 FAUCET_URL=http://localhost:$FAUCET_PORT
-linera_spawn linera net up --with-faucet --faucet-port $FAUCET_PORT
+linera_spawn linera net up --policy-config testnet --with-faucet --faucet-port $FAUCET_PORT
 
 # If you're using a testnet, run this instead:
 #   LINERA_TMP_DIR=$(mktemp -d)