Remove duplicate line in setup.cfg (#9380)

setup.cfg

@@ -34,7 +34,6 @@ ignore =
     F401  # module imported but unused
     W504  # line break after binary operator
     E127  # continuation line over-indented for visual indent
-    W504  # line break after binary operator
     E231  # missing whitespace after ‘,’, ‘;’, or ‘:’
     E501  # line too long
     F403  # ‘from module import *’ used; unable to detect undefined names