bump pinned version of black

[cs01]

• [] I have added an entry to CHANGELOG.md, or an entry is not needed for this change
  No changelog entry needed

Summary of changes

Pin version of black to avoid error

Traceback (most recent call last):
  File "/home/runner/work/gdbgui/gdbgui/.nox/lint/bin/black", line 5, in <module>
    from black import patched_main
  File "/home/runner/work/gdbgui/gdbgui/.nox/lint/lib/python3.9/site-packages/black/__init__.py", line 52, in <module>
    from typed_ast import ast3, ast27
  File "/home/runner/work/gdbgui/gdbgui/.nox/lint/lib/python3.9/site-packages/typed_ast/ast3.py", line 40, in <module>
    from typed_ast import _ast3
ImportError: /home/runner/work/gdbgui/gdbgui/.nox/lint/lib/python3.9/site-packages/typed_ast/_ast3.cpython-39-x86_64-linux-gnu.so: undefined symbol: _PyUnicode_DecodeUnicodeEscape

See python/typed_ast#169

Test plan

Tested by running

nox -s lint

and CI on pull request passes