unattended-upgrades: Only send an email on errors

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

unattended-upgrades/50unattended-upgrades.Debian.bullseye

@@ -62,7 +62,7 @@ Unattended-Upgrade::Mail "root";
 
 // Set this value to "true" to get emails only on errors. Default
 // is to always send a mail if Unattended-Upgrade::Mail is set
-//Unattended-Upgrade::MailOnlyOnError "true";
+Unattended-Upgrade::MailOnlyOnError "true";
 
 // Remove unused automatically installed kernel-related packages
 // (kernel images, kernel headers and kernel version locked tools).

unattended-upgrades/50unattended-upgrades.Debian.buster

@@ -63,7 +63,7 @@ Unattended-Upgrade::Mail "root";
 
 // Set this value to "true" to get emails only on errors. Default
 // is to always send a mail if Unattended-Upgrade::Mail is set
-//Unattended-Upgrade::MailOnlyOnError "true";
+Unattended-Upgrade::MailOnlyOnError "true";
 
 // Remove unused automatically installed kernel-related packages
 // (kernel images, kernel headers and kernel version locked tools).