Unpin pytest version

[rhysyngsun]

What are the relevant tickets?

Closes #124

Description (What does it do?)

I have two commits here:

• The first is a commit with changes to support a docker-compose container that has pants setup. I've been running into obtuse issues on my local machine with their binaries so I needed to do this just to work on the issues.
• The second commit is the actual fix here - it overrides the package distribution's pytest requirement to be any version above 7, but still permits the project itself to be more opinionated and even differ for running tests.

How can this be tested?

• Run pants package ::
• Run pip install pkginfo on your host system to easily inspect the package.
• Run pkginfo dist/mitol_django_common-2023.1.17-py3-none-any.whl, you should see output like this indicating the new pytest requirements as mentioned above:

requires_dist: ['django-redis (~=5.0.0)', 'django-webpack-loader (>=0.7.0)', 'django (<4.0,>=2.2.12)', 'factory-boy (~=3.2)', 'pytest (>=7.0.0)', 'pytz (>=2020.4)', 'requests (>=2.20.0)', 'setuptools', 'typing-extensions']

[mbertrand]

LGTM, works with and w/out docker; and it's great to have the docker option now 👍