Jon Tejnung

This plugin will give you three alternatives for managing your WordPress updates:
<ul>
<li>Update automatically – This updates WordPress/themes/plugins automatically and sends an email to the site admin when an update has been performed.</li>
<li>Update automatically (no email) – Same as the first alternative, but without the email.</li>
<li>Inform about updates once a week – This will send an email to the admin once a week if there are anything that can be updated.</li>
</ul>
Notice that only plugins/themes that resides in the WordPress 
repository will be updated/informed about.
The plugin has not been tested and is not primarily made for multi site-installations.

Simple Automatic Updates

Activate automatic updates or weekly notifications for the site.

Scott Reilly

This plugin removes the WordPress update nag that appears at the top of all admin pages when a new version of WordPress is released.
Tired of WordPress nagging you about a new release? Maybe you already know about it and want to hold off on an update and would rather not see the update nag on every admin page you visit. Activate this plugin and be bothered no more!
The status of your version of WordPress (be it current or out-of-date) is still reflected in the footer of your admin pages and in the update count link in the admin bar.
And certainly, of course, I don’t advocate completely ignoring the fact that updates often contain fixes for critical bugs or exploits. However, there are various other means of learning about updates; and once known, not everyone is able or willing to update immediately.
Links: <a href="https://coffee2code.com/wp-plugins/no-update-nag" rel="nofollow ugc">Plugin Homepage</a> | <a href="https://wordpress.org/plugins/no-update-nag/" rel="ugc">Plugin Directory Page</a> | <a href="https://github.com/coffee2code/no-update-nag/" rel="nofollow ugc">GitHub</a> | <a href="https://coffee2code.com" rel="nofollow ugc">Author Homepage</a>

No Update Nag

does what it says on the tin

Removes the WordPress update nag that appears at the top of all admin pages when a new version of WordPress is released.

Simple Automatic Updates vs No Update Nag