maint: simplify flake8 config

.flake8

@@ -1,13 +1,11 @@
+# flake8 is used for linting Python code setup to automatically run with
+# pre-commit.
+#
+# ref: https://flake8.pycqa.org/en/latest/user/configuration.html
+#
 [flake8]
-# Ignore style and complexity
 # E: style errors
 # W: style warnings
 # C: complexity
-# F401: module imported but unused
-# F403: import *
-# F811: redefinition of unused `name` from line `N`
-# F841: local variable assigned but never used
-# E402: module level import not at top of file
-# I100: Import statements are in the wrong order
-# I101: Imported names are in the wrong order. Should be
-ignore = E, W, C, F401, F403, F811, F841, E402, I100, I101, D400
+# D: docstring warnings (unused pydocstyle extension)
+ignore = E, C, W, D