Fix ./mach clippy.

Fixes https://github.com/servo/servo/issues/13117.

python/servo/devenv_commands.py

@@ -105,7 +105,7 @@ class MachCommands(CommandBase):
         '--json', '-j', action="store_true",
         help='Outputs')
     def clippy(self, package=None, json=False):
-        params = ["--features=script/plugins/clippy"]
+        params = ["--features=clippy"]
         if package:
             params += ["-p", package]
         if json: