Setting up development environment via requirements currently broken for Python >=3.10

[rossbar]

I failed to update the deepcell-toolbox dependency in requirements.txt for the 0.12.4 release - this means that setting up a development environment with pip (i.e. pip install -r requirements.txt) is currently broken.

This shouldn't affect end-users, so I'm going to hold off making another patch release to fix it unless there is a strong desire to do so. There is another release on the horizon which will fix this along with many other issues. The quick fix for developers: in requirements.txt, update the deepcell-toolbox~=0.11.2 line to deepcell-toolbox~=0.12.0.

[rossbar]

This likely only affects developers on Python3.10 which is not yet supported.