fix flake8 config (pydata#7321)

* fix flake8 config

* reformat

Author: mathause

setup.cfg

@@ -147,11 +147,12 @@ markers =
 
 [flake8]
 ignore =
-    E203 # whitespace before ':' - doesn't work well with black
-    E402 # module level import not at top of file
-    E501 # line too long - let black worry about that
-    E731 # do not assign a lambda expression, use a def
-    W503 # line break before binary operator
+    # E203: whitespace before ':' - doesn't work well with black
+    # E402: module level import not at top of file
+    # E501: line too long - let black worry about that
+    # E731: do not assign a lambda expression, use a def
+    # W503: line break before binary operator
+    E203, E402, E501, E731, W503
 exclude =
     .eggs
     doc