Unable to delete .pkg files in /Library/Updates/
Reboot in Recovery mode by restarting your Mac and holding Command+R. It can take more time to boot as
  usual, that's OK, just be patient.
  In the top menu go to Utilities and open Terminal.
  Type csrutil disable and press Enter.
  Type reboot and press Enter to reboot again.
  


Now delete the update .pkgs but the .plist files will contain wrong info, if any, about the download status etc. I am not sure if they have to be deleted or not.

&lt;key&gt;InstallAtLogout&lt;/key&gt;
    &lt;array/&gt;
    &lt;key&gt;ProductPaths&lt;/key&gt;
    &lt;dict&gt;
        &lt;key&gt;061-41421&lt;/key&gt;
        &lt;string&gt;061-41421&lt;/string&gt;
    &lt;/dict&gt;


Also, disable automatic download from System Preferences  → Software Updates. 


  Now you should re-enable System Integrity Check. It is there for a
  reason.
  
  
  Reboot in Recovery mode by restarting your Mac and holding Command+R.
  In the top menu go to Utilities > Terminal.
  Type csrutil enable and press Enter.
  Type reboot and press Enter to reboot again.
  


How to completely disable Siri on Sierra?