Only send upgrade reminders to learners who are eligible to upgrade

Updating edx-enterprise requirement to 0.53.1.

Merge PR 16260 back into master with a fix for the course sock

set django version in paver args

https://github.com/edx/edx-enterprise/compare/0.53.0...0.53.1

[ENT-432] Bump edx-enterprise to 0.53.0.

fix malformed template variable

Revert "LEARNER-717 Added logs for discovery"

Harry rein/responsive dashboard

[ENT-671] Show the Enterprise tagline on the logistration page.

Cale/refactor upgrade email resolvers

This reverts commit b541dfa3.