fix(spiders): corrections and removal of dead code

scrapling/spiders/checkpoint.py

@@ -32,7 +32,7 @@ class CheckpointManager:
         if not isinstance(interval, (int, float)):
             raise TypeError("Checkpoints interval must be integer or float.")
         else:
-            if interval < 0:
+            if interval <= 0:
                 raise ValueError("Checkpoints interval must be greater than 0.")
 
     async def has_checkpoint(self) -> bool: