Change middleware to always be new-style.
Review Request #11961 — Created Jan. 21, 2022 and submitted — Latest diff uploaded
With Djblets 3.x using only Django 3.2+, we no longer need to deal with
old-style middleware or theMIDDLEWARE_CLASSESsetting. This change
updates things to always use the new style.
Ran unit tests.