plugins/elements/gsttypefindelement.c: Use gst_type_find_helper_get_range() here, so we can honour the min-probabilit...

Original commit message from CVS:
* plugins/elements/gsttypefindelement.c:
(gst_type_find_element_activate):
Use gst_type_find_helper_get_range() here, so we
can honour the min-probability property and also emit
the signal with the correct probability of the found caps.