Improved authentication metrics.

This adds a graded icon for LTI units. This was meant to go into
a recent commit, but I only updated github.in not the txt requirement
files.

AA-75

This adds a missing migration file to change the plural name of a
model.

These were pinned because they drop support for Django<2.2 (or were
planning on it, in the latter case.)

No related changes in computed requirements.

ARCHBOM-1105

TNL-7184

and settings to set SameSite=None for all secure cookies.

This update pulls in transitioning various contains content calls to
use the new enterprise catalog service behind a waffle flag.

ENT-2575

This adds contraints to:
kiwisolver: next release only works with python>=3.6

The was run to upgrade:
django-splash
django-wiki
edx-search
The previous versions were constraining django below 2.0.

Co-authored-by: Robert Raposa <rraposa@edx.org>

This adds django admin access to its models.

AA-93

removed extra dependency