mod/lti/lang/en/lti.php contains references to imsroleadmin and imsroleinstructor which do not appear to be used anywhere. If this is in fact the case we should remove them in 2.3.

It is probably a bad idea to remove them in current versions as this is more of an improvement than a fix and there is the small possibility that somebody could be calling these in code external to Moodle.