toaster-requirements.txt: require Django 2.2
In commit 9730f95686b2ac72cf1fa513c555f7c7787e2667
Django 2.2 was enabled.
Django 1.11 was EOL on April 1, 2020
Signed-off-by: Tim Orling <timothy.t.orling@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit ee15e78c6f9b59c221b1e43973ee4db20c5b443b)
Signed-off-by: Steve Sakoman <steve@sakoman.com>