[doc] Improve manpage
[doc] Improve manpage

as suggested by:
%  mandoc -Tlint doc/ledger.1

[ci skip]

jwakely/ledger,ledger/ledger,afh/ledger,paulbdavis/ledger,duncanmortimer/ledger,duncanmortimer/ledger,jwakely/ledger,paulbdavis/ledger,ledger/ledger,ledger/ledger,jwakely/ledger,duncanmortimer/ledger,afh/ledger,paulbdavis/ledger,duncanmortimer/ledger,jwakely/ledger,paulbdavis/ledger,duncanmortimer/ledger,paulbdavis/ledger,jwakely/ledger,afh/ledger,ledger/ledger,ledger/ledger,duncanmortimer/ledger,duncanmortimer/ledger,jwakely/ledger,jwakely/ledger,paulbdavis/ledger,afh/ledger,paulbdavis/ledger,afh/ledger