Bug#996854: Mention that "install" indeed does accept filenames after all

[積丹尼 Dan Jacobson <jidanni@jidanni.org>]

Package: apt
Version: 2.3.10
File: /usr/share/man/man8/apt-get.8.gz

man apt-get says:
       install
           install is followed by one or more packages desired for
           installation or upgrading. Each package is a package name, not a
           fully qualified filename

All I know is
apt-get install ./Webex.deb
apt-get install $PWD/Webex.deb
worked fine.