Drop an attempted comment from flake8 config in setup.cfg

This fails at least when run via tox on current Fedora, flake8
tries to parse the # as a directive and chokes on it.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

setup.cfg

@@ -23,4 +23,5 @@ addopts = --cov mwclient test
 [flake8]
 max-line-length = 90
 ignore = 
-	W503  # Line break before binary operator
+    # Line break before binary operator
+    W503