Instructions for running test suite are incomplete

[engma-linguistics]

Describe the bug
The requirements for requirements-test.txt do not include required Django packages, and installing them anyways as from requirements.txt leads to incompatibility issues because of an old version of fakeredis being used incompatible with the requirements.txt version of redis.
Attempting to forge ahead anyways leads to the following error:
pytest-django could not find a Django project (no manage.py file could be found). You must explicitly add your Django project to the Python path to have it picked up.
To Reproduce
Steps to reproduce the behavior:

1. Go to https://github.com/heartexlabs/label-studio#run-test-suite
2. Attempt to reproduce in a new environment

Expected behavior
A clear and followable set of instructions to set up the test suite and be able to run it

Environment (please complete the following information):

• OS: ubuntu 20.04
• Label Studio Version 1.7