For some reason, the content of categorical/subsref.m (true path of the file is the output of fullfile(matlabroot, 'toolbox', 'matlab', 'datatypes', '@categorical', 'subsref.m')) has been edited. Line 20 of that file is not what it should be. it looks like somebody was trying to debug the file and left some debug code there. That debug code makes no sense as in most cases it will error and in the rare cases where it doesn't, will output nonsense.
As it's unknown what else has been modified, I would recommend you reinstall matlab unfortunately.
And of course, never modify matlab own m files.