Bug#622190: release-notes: Update "The stable-updates section" with new information from the wiki

[Dmitry Semyonov <linulin@gmail.com>]

Package: release-notes
Severity: normal

http://wiki.debian.org/StableUpdates contains the following important
note:

Note that if APT::Default-Release is set in your /etc/apt/apt.conf (or
in any of /etc/apt/apt.conf.d/*), then, in order for automatic upgrades
to work, it is necessary to add the following configuration block into
/etc/apt/preferences, (see AptPreferences for more information):

Package: *
Pin: release n=squeeze-updates
Pin-Priority: 990