debugcommands: fix a missing b prefix
This wasn't causing any immediate problems because of the source
transformer, but I noticed the inconsistency and it bugged me.
# skip-blame just a b prefix
Differential Revision: https://phab.mercurial-scm.org/D4255
%include map-cmdline.default
[templates]
changeset = '{cset}{branches}{bookmarks}{tags}{lphase}{parents}{luser}{ldate}{summary}\n'
changeset_verbose = '{cset}{branches}{bookmarks}{tags}{lphase}{parents}{luser}{ldate}{lfiles}{lfile_copies_switch}{description}\n'