typing: suppress a few attribute errors in url.py
These are newly detected by pytype 2022.03.21. Not sure what is going on here-
`realhostport` and `headers` are added outside of the constructor, so that makes
sense. But PyCharm also thinks the private methods don't exist, though when
clicking through the class hierarchy, it shows in the py3.9 source code.
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
end_of_line = lf
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
end_of_line = lf
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false
end_of_line = lf