Remove redundant `mock` dev-dependency

[rszamszur]

• I have searched the issues of this repo and believe that this is not a duplicate.

Feature Request

Since mock is now (well it is already for a long time, but I've missed this somehow 😄 ) part of the Python standard library, available as unittest.mock in Python 3.3 onwards. It can be removed from pyproject.toml dev-dependencies.

To remove:
https://github.com/rszamszur/fastapi-mvc/blob/d0c30b77cb243d1833a4263274d230f64b513c38/pyproject.toml#L42

Lastly update mock import in test cases:

$ grep -rl "import mock" {{cookiecutter.folder_name}}
{{cookiecutter.folder_name}}/tests/unit/app/exceptions/test_http.py
{{cookiecutter.folder_name}}/tests/unit/app/test_asgi.py
{{cookiecutter.folder_name}}/tests/unit/app/utils/test_redis.py
{{cookiecutter.folder_name}}/tests/unit/cli/test_serve.py
{{cookiecutter.folder_name}}/tests/unit/cli/test_utils.py
{{cookiecutter.folder_name}}/tests/unit/test_wsgi.py