Use en_US dictionary

It also contains British English terms, so it accepts them. ENforcing
them is up to reviewers.

tox.ini

@@ -44,7 +44,7 @@ commands =
     poetry run black aleksis/
 
 [flake8]
-dictionaries=en_GB,python,technical,django
+dictionaries=en_US,python,technical,django
 max_line_length = 100
 exclude = migrations,tests
 ignore = BLK100,E203,E231,W503,D100,D101,D102,D103,D104,D105,D106,D107,RST215,RST214,F821,F841,S106,T100,T101,DJ05