Set max line length to 88 (same as black's default)

setup.cfg

@@ -17,7 +17,7 @@ test = pytest
 ignore_missing_imports = True
 
 [flake8]
-max-line-length = 80
+max-line-length = 88
 ignore =
     # See the black style guide for more info:
     # https://github.com/psf/black/blob/master/docs/the_black_code_style.md