Bug#864848: Should not talk about hd-media - that's armhf only

[Steve McIntyre <steve@einval.com>]

Package: installation-guide-armel
Severity: normal

As seen in

  https://www.debian.org/releases/jessie/armel/ch05s01.html.en

there's discussion of "unpack the hd-media tarball". This doesn't
exist on armel...

-- System Information:
Debian Release: 9.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-3-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)