Fix apidoc of pw.io.subscribe (#5866)

GitOrigin-RevId: 45db6290865283ac3fcdc0f88092e8df663c2b62

python/pathway/io/_subscribe.py

@@ -22,10 +22,10 @@ def subscribe(
     Args:
         table: the table to subscribe.
         on_change: the callback to be called on every change in the table. The
-          function is required to accept three parameters: the row changed, the time
+          function is required to accept four parameters: the key, the row changed, the time
           of the change in microseconds and the flag stating if the change had been an
           addition of the row. These parameters of the callback are expected to have
-          names row, time and is_addition respectively.
+          names key, row, time and is_addition respectively.
         on_end: the callback to be called when the stream of changes ends.
         on_time_end: the callback function to be called on each closed time of computation.
     Returns: