actions: rename DEFICIENCY constant to FORMAT_VARIANT
It was not obvious what does deficieny means and every format change can't be a
deficiency. There are some format changes like compression levels, share-safe
which can't be understood at deficiencies.
This patch renames the constant to make things clearer.
Differential Revision: https://phab.mercurial-scm.org/D9664
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true