Set version pins for Python 3.7.7 docker image.

[sonoransun]

Description

Due to issues with Python and package repositories in this Docker image, we have to revert version pins back a major version. Attempting to update pip itself, which is also out of date, did not resolve the issue.

References: https://meedan.atlassian.net/browse/CV2-6218

How to test?

Verify with a successful deployment to QA.

Checklist

• I have performed a self-review of my code and ensured that it is safe and runnable, that code coverage has not decreased, and that there are no new Code Climate issues. I have also followed Meedan's internal coding guidelines.

[dmou]

I assume it's not worth updating the CI image to 3.8?

[sonoransun]

I assume it's not worth updating the CI image to 3.8?

As I recall this version (3.8) pulled in some other version hell, and we stick with 3.7 to avoid having to do further troubleshooting.