Updated usage comments in 'bootstrap-network.sh'

[stevenengler]

See ticket #33023.

The usage comment says the following:

# Usage:
#    tools/bootstrap-network.sh [network-flavour]
#    network-flavour: one of the files in the networks directory,
#                     (default: 'basic')

but the actual code says the following:

# Set the variables for the chutney network flavour
export NETWORK_FLAVOUR=${NETWORK_FLAVOUR:-"bridges+hs-v2"}
[ -n "$1" ] && { NETWORK_FLAVOUR=$1; shift; }
export CHUTNEY_NETWORK="$CHUTNEY_PATH/networks/$NETWORK_FLAVOUR"

As you can see, the comments say that the default network is 'basic', but the code actually starts 'bridges+hs-v2'.