message: test: use f-strings in feature_settings.py
diff: @@ -83,7 +83,7 @@ class SettingsTest(BitcoinTestFramework):
  with altsettings.open("w") as fp:
  fp.write('{"key": "value"}')
  with node.assert_debug_log(expected_msgs=['Setting file arg: key = "value"']):
  - self.start_node(0, extra_args=["-settings={}".format(altsettings)])
  + self.start_node(0, extra_args=[f"-settings={altsettings}"])
  self.stop_node(0)
  