Tell flake-quote we're using double quotes

I have recently installed this plugin locally.

Author: peterjc

.flake8

@@ -7,3 +7,9 @@ extend-ignore =
     # See https://github.com/PyCQA/pycodestyle/issues/373
     # flake8/pycodechecker give false positives on black code
     E203,
+
+# =====================
+# flake-quote settings:
+# =====================
+# Set this to match black style:
+inline-quotes = double