Today, I received an email from my server, notifying me of an updated version of Piwik being available. That's nice I thought, but the thing is that I never received such an email before, and I couldn't recall seeing any setting in Piwik's UI for configuring the same!
After a bit of searching around the net, I found that this setting was probably added with Piwik 2.4.0, at least that's when I started getting the notifications.
Anyway, if you don't want Piwik to send update notification emails for whatever reason, you can follow the given instructions.
Disabling all (core + plugins) update notification emails
By default, update notification emails are only enabled for Piwik's core, i.e., the main installation, and disabled for the plugins.
To disable updates to the Piwik core as well, you need to edit the
config.ini.php file, present under the config directory of your Piwik installation.