MAINT: remove nox configuration

nox is not used by any of the current maintainers and its
configuration is becoming outdated. Instead of trying to keep it
updated without any effective testing, remove it.

Author: dnicolodi

docs/spelling_wordlist.txt

@@ -11,7 +11,6 @@ executables
 frontend
 Github
 macOS
-nox
 Numpy
 pre
 pluggy