calrify type of pitch constructor argument

Line 1926 says that the argument can be a Pitch too so the constructor should reflect that

music21/pitch.py

@@ -1909,7 +1909,7 @@ class Pitch(prebase.ProtoM21Object):
     }
 
     def __init__(self,
-                 name: str|int|float|None = None,
+                 name: str|int|float|Pitch|None = None,
                  *,
                  step: StepName|None = None,
                  octave: int|None = None,