mdiff: tweak calls into `bdiff.fixws` to match its type hints
It turns out that protocol classes can be used for modules too, which is great
because all of the dynamically loaded modules (and their attributes) are
currently inferred as `Any`. See the next commit for details.
A protocol class for the `bdiff` module detected this (trivial) mismatch, so
correct it first. The various implementations of this method are typed as
taking a `bool`. The `cext` implementation parses its arguments with
`PyArg_ParseTuple(args, "Sb:fixws", &s, &allws)`, which wants an `int`. But
experimenting in `hg debugshell` under py38, passing `True` or `False` to
`cext.fixws()` also works. We can change the implementation to use "p" (which
was introduced in py33) instead of "b", but that's beyond the scope of this.
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL