Tours are part of core code for Moodle. Probably best not to un-install but to hide in order to avoid un-pleasant/un-expected changes to behavior of Moodle.
Firist, see if the usertours directory is still present in your code directory.
should be in moodlecode/admin/tool/usertours/
IF not ... here's a suggestion .... let's say your code is in /var/www/html/ ... leave that alone and as is.
cd /var/www/ and 'side load' (download) a copy of the version of the code of Moodle you have into a 'sideload' directory. The copy the sideload/admin/tool/usertours directory to the active code directory in /var/www/html/admin/tool/usertours
Check ownership/permissions on the usertours directory you copied and make sure those match the other directory/file ownerships/permissions.
Then try to login. Hopefully, Moodle will allow you to login or throw you into an install thing for usertours.
As long as usertours is on ... ie, not hidden ... it applies to all users ... including admins.
So if you do not desire to use it, simply hide it (open eye to closed eye).
'spirit of sharing', Ken