[options] fix passing negative numbers as arguments (#5262)

https://github.com/mikf/gallery-dl/issues/5262#issuecomment-2468677453

fixes regression introduced in 9e729681

'argparse' sets a flag and changes its behavior when using something
that looks like a negative number as option string, '-4' and '-6' in
this case.

gallery_dl/option.py

@@ -803,4 +803,10 @@ def build_parser():
               "&& convert * ../doc.pdf\""),
     )
 
+    try:
+        # restore normal behavior when adding '-4' or '-6' as arguments
+        parser._has_negative_number_optionals.clear()
+    except Exception:
+        pass
+
     return parser