Fix a tiny typo in _Step docstring (#1051)

Co-authored-by: plaguss <[email protected]>

src/distilabel/steps/base.py

@@ -168,7 +168,7 @@ def process(self, inputs: StepInput) -> StepOutput:
 
         class StepWithSeveralPreviousStep(Step):
             # mind the * to indicate that the argument is a list of StepInput
-            def process(self, inputs: *StepInput) -> StepOutput:
+            def process(self, *inputs: StepInput) -> StepOutput:
                 yield [...]
         ```