fix: Disable flake8 w503

[dciborow]

When using black to autoformat an extension one flake8 rule fails on a rule which does not follow pep8. W503 is disabled by default, but because the .flake8 files are using "ignore" instead of "extend-ignore", W503 is enabled in our ruleset. The maintainer of flake8 explained here I recommend that we disable this rule, so that people may follow pep8 while also being able to use black to autoformat their code.

Line break occurred before a binary operator (W503)

This rule goes against the PEP 8 recommended style, which was changed on April 16th, 2016 in [this commit](https://github.com/python/peps/commit/c59c4376ad233a62ca4b3a6060c81368bd21e85b). The tool [will soon be updated](https://github.com/PyCQA/pycodestyle/pull/502) to recommend the opposite: line breaks should occur before the binary operator because it keeps all operators aligned.

Code Before Autoformat

    def is_equal(self, other):
        return (
            self.__class__ == other.__class__ and
            self.type == other.type and
            self.name == other.name and
            self.email == other.email and
            self.phone == other.phone and
            self.uri == other.uri
        )

Code After Autoformat

    def is_equal(self, other):
        return (
            self.__class__ == other.__class__
            and self.type == other.type
            and self.name == other.name
            and self.email == other.email
            and self.phone == other.phone
            and self.uri == other.uri
        )

Flake8 Output

Running flake8 on extensions...
/workspaces/partnercenter-cli-extension/partnercenter/azext_partnercenter/models/listing_contact.py:29:13: W503 line break before binary operator
/workspaces/partnercenter-cli-extension/partnercenter/azext_partnercenter/models/listing_contact.py:30:13: W503 line break before binary operator
/workspaces/partnercenter-cli-extension/partnercenter/azext_partnercenter/models/listing_contact.py:31:13: W503 line break before binary operator
/workspaces/partnercenter-cli-extension/partnercenter/azext_partnercenter/models/listing_contact.py:32:13: W503 line break before binary operator
/workspaces/partnercenter-cli-extension/partnercenter/azext_partnercenter/models/listing_contact.py:33:13: W503 line break before binary operator
5     W503 line break before binary operator

[wangzelin007]

Personally, I prefer this format:

    def is_equal(self, other):
        return (
            self.__class__ == other.__class__
            and self.type == other.type
            and self.name == other.name
            and self.email == other.email
            and self.phone == other.phone
            and self.uri == other.uri
        )