dirstate: remove obsolete comment from setbranch
This comment should have been removed in
b74361cf7c0a, when the call
to scmutil.checknewlabel was removed.
commands: 'hg bookmark NAME' should work even with ui.strict=True
Before this patch, enabling strict command processing (ui.strict=True)
meant that 'hg bookmark NAME', as referenced several places in the
documentation, would not work. This adds 'bookmark' as an explicit alias
to 'bookmarks'.