style: ruff format and the lint rules of the driver standard

Mechanical: ruff format, and ruff check --fix with the rule set every NAPALM
driver uses (E, F, I, UP, B at line length 100, Python 3.10). What ruff
cannot fix comes in the next commit.

napalm_openwrt/routing_mixin.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -145,7 +144,7 @@ class OpenWrtRoutingMixin:
             # "192.168.1.0/24 dev ..." → prefix as-is
             if line_s.startswith("default"):
                 prefix = "0.0.0.0/0"
-                rest = line_s[len("default"):].strip()
+                rest = line_s[len("default") :].strip()
             else:
                 parts = line_s.split()
                 prefix = parts[0]