re.MULTILINE is erroneously passed as the `count` positional argument in re.sub

[asottile-sentry]

in python 3.13 with warnings enabled this becomes an error:

.venv/lib/python3.13/site-packages/email_reply_parser/__init__.py:32: in parse_reply
    return EmailReplyParser.read(text).reply
.venv/lib/python3.13/site-packages/email_reply_parser/__init__.py:22: in read
    return EmailMessage(text).read()
.venv/lib/python3.13/site-packages/email_reply_parser/__init__.py:68: in read
    self.text = re.sub('([^\n])(?=\n ?[_-]{7,})', '\\1\n', self.text, re.MULTILINE)
/opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/re/__init__.py:203: in sub
    warnings.warn(
E   DeprecationWarning: 'count' is passed as positional argument

the code clearly didn't intend to do what it's doing -- right now it's passing count=8 because re.MULTILINE has the integer value 8

I think the parameter can be dropped entirely since the regex used does not utilize ^ or $ (which is what MULTILINE changes the behaviour of)