Fix `make tag` workflow

[jamescooke]

Current behaviour

make tag fails in default dev environment on py310 as a result of not having asttokens installed:

git tag -a $(python -c 'from src.flake8_aaa.__about__ import __version__; print("v{}".format(__version__))')
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/james/active/flake8-aaa/src/flake8_aaa/__init__.py", line 1, in <module>
    from .checker import Checker
  File "/home/james/active/flake8-aaa/src/flake8_aaa/checker.py", line 5, in <module>
    import asttokens
ModuleNotFoundError: No module named 'asttokens'

Expected behaviour

Fix make tag so the release process is easy again.

[jamescooke]

Fixed in #233