Edit 3: @ElCanario's answer is providing a better solution.
Edit 2: Don't do this. See Florian's comment below.
Edit: This will remove the user from the wheel group, stopping updates without using a password. After that a reboot is required. Now the user should be able to still install software after being prompted his/her password, but I have not tested this. I am not sure you really want to remove yourself from group wheel
.
A solution for removing the user from group wheel is being provided at StackExchange:
# gpasswd -d user group
in your example:
# gpasswd -d markusam wheel
If you are very careful, you may remove the username from the line starting with wheel:x:
in /etc/group
. Be sure to make a backup and not change anything else.
Edit: Removing the user from the wheel group may have other implications too. You may e.g. loose access to the system journal.