[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

hoomd_validation/workflow.py

@@ -79,7 +79,7 @@ def add_action(cls, name, action):
             raise ValueError(message)
 
         if 'products' not in action._configuration:
-            warnings.warn(f"Action {name} is missing products.", stacklevel=2)
+            warnings.warn(f'Action {name} is missing products.', stacklevel=2)
 
         cls._actions[name] = action