Remove use of balance --average since it doesn't work
Remove use of balance --average since it doesn't work

Currently the docs recommend the use of balance --average to help
generate a budget.  Apparently that doesn't work.  Instead use the
register command with --average.

ledger/ledger,afh/ledger,ledger/ledger,afh/ledger,afh/ledger,ledger/ledger,ledger/ledger,afh/ledger,afh/ledger,ledger/ledger