Improve constraint comments and tasking

[robrap]

Improve the comments and tasking for constraints in https://github.com/openedx/edx-platform/blob/master/requirements/constraints.txt to make it simpler to track how and when constraints could be removed.

• Read Update OEP-18 Python Dependency Management with more constraint tips open-edx-proposals#332 for some ideas.
  • This work is not blocked on the OEP proposal, and better yet, would help prove out what the proposal might be.
• My hypothesis is that including dates in the comments would make it simpler to spot really outdated constraints.
• What constraint removal do we want to task or not-task? For example, maybe Django upgrades don't need to be tasked, or maybe we have epic for future upgrade work?
• We don't have to land all updates at once. We could iteratively improve this file. But, the sooner the better, so that others might copy/paste the patterns.
• Consider adding additional README docs for what to do at the top of the file.
• Once this work is done, consider ticketing the same work to update common_constraints.txt as well.

[jristau1984]

@iamsobanjaved the hope is that Arbi-BOM can field this ticket, does that sound reasonable?

[iamsobanjaved]

is this issue a duplicate of #35055 ?

[robrap]

Thanks @iamsobanjaved. I guess I forgot and couldn't find this when I re-tasked. Closing this ticket in favor of #35055.