mangler: stop rewriting string constants to be bytes literals
We've rewritten everything, so we no longer require this step.
Differential Revision: https://phab.mercurial-scm.org/D6973
[tool.black]
line-length = 80
exclude = 'build/|wheelhouse/|dist/|packages/|\.hg/|\.mypy_cache/|\.venv/|mercurial/thirdparty/|hgext/fsmonitor/pywatchman/|contrib/python-zstandard/'