remove default left-right print margins per upstream h5bp change

Refs:
    https://github.com/h5bp/html5-boilerplate/commit/57be193031b95b003b96efe9eba7a4db7f58f4e1
    https://github.com/h5bp/html5-boilerplate/issues/1477
Merge pull request #12250 from twbs/rm-print-margins

remove default left-right print margins per upstream h5bp change