rust-status: fix thread count ceiling
This was forcing 16 threads instead of creating a ceiling, which is wrong
when either the available parallelism of the platform is lower or when
the user wants to set it explicitly (like we do in `run-tests.py`)
# Files that just need to be migrated to the formatter.
# Do not add new files here!
mercurial/cext/manifest.c
mercurial/cext/osutil.c
# Vendored code that we should never format:
syntax: glob
contrib/python-zstandard/**.c
contrib/python-zstandard/**.h
hgext/fsmonitor/pywatchman/**.c
mercurial/thirdparty/**.c
mercurial/thirdparty/**.h
mercurial/pythoncapi_compat.h