Remove unneeded vacuum_delay_point from heap_vac_scan_get_next_block

heap_vac_scan_get_next_block() does relatively little work, so there
is no need to call vacuum_delay_point(). A future commit will call
heap_vac_scan_get_next_block() from a callback, and we would like to
avoid calling vacuum_delay_point() in that callback.

Author: Melanie Plageman
Discussion: https://postgr.es/m/CAAKRu_Yf3gvXGcCnqqfoq0Q8LX8UM-e-qbm_B1LeZh60f8WhWA%40mail.gmail.com

src/backend/access/heap/vacuumlazy.c

@@ -1233,7 +1233,6 @@ find_next_unskippable_block(LVRelState *vacrel, bool *skipsallvis)
 			*skipsallvis = true;
 		}
 
-		vacuum_delay_point();
 		next_unskippable_block++;
 	}