filectx: remove __new__
It does not seem to be used anywhere, and breaks a later patch.
#require test-repo pyflakes hg10
$ . "$TESTDIR/helpers-testrepo.sh"
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate 'set:**.py or grep("^#!.*python")' -X hgext/fsmonitor/pywatchman \
> -X mercurial/pycompat.py -X contrib/python-zstandard \
> 2>/dev/null \
> | xargs pyflakes 2>/dev/null | "$TESTDIR/filterpyflakes.py"
tests/filterpyflakes.py:39: undefined name 'undefinedname'