If the enrolment instance (the 'published resource') has been upgraded
from LTI 1.1/2.0 to LTI 1.3 (i.e. a new instance was not created),
prevent legacy launches which may occur from old resource links. Only
LTI Advantage launches should be permitted through the method.
dirname() is a slow function compared with __DIR__ and using
'/../'. Moodle has a large number of legacy files that are included
each time a page loads and is not able to use an autoloader as it is
functional code. This allows those required includes to perform as
best as possible in this situation.