Increase assignment upload limit from 4MB to 20MB (#21589)
Increase assignment upload limit from 4MB to 20MB (#21589)

Due to a request from a Master's partner who reports
that the current 4MB limit is not enough for their
degree programs.

EDUCATOR-4635
EDUlib/edx-platform,cpennington/edx-platform,edx-solutions/edx-platform,arbrandes/edx-platform,edx-solutions/edx-platform,msegado/edx-platform,EDUlib/edx-platform,eduNEXT/edx-platform,eduNEXT/edunext-platform,ESOedX/edx-platform,appsembler/edx-platform,mitocw/edx-platform,cpennington/edx-platform,arbrandes/edx-platform,edx-solutions/edx-platform,arbrandes/edx-platform,ESOedX/edx-platform,stvstnfrd/edx-platform,ESOedX/edx-platform,appsembler/edx-platform,edx-solutions/edx-platform,angelapper/edx-platform,msegado/edx-platform,angelapper/edx-platform,stvstnfrd/edx-platform,eduNEXT/edx-platform,cpennington/edx-platform,eduNEXT/edx-platform,eduNEXT/edunext-platform,angelapper/edx-platform,EDUlib/edx-platform,msegado/edx-platform,mitocw/edx-platform,eduNEXT/edunext-platform,cpennington/edx-platform,arbrandes/edx-platform,ESOedX/edx-platform,stvstnfrd/edx-platform,mitocw/edx-platform,eduNEXT/edx-platform,eduNEXT/edunext-platform,stvstnfrd/edx-platform,msegado/edx-platform,EDUlib/edx-platform,mitocw/edx-platform,edx/edx-platform,appsembler/edx-platform,angelapper/edx-platform,msegado/edx-platform,edx/edx-platform,edx/edx-platform,edx/edx-platform,appsembler/edx-platform