regexp: use built-in clear to clear b.visited in *bitState.reset

Change-Id: I1a723124f7050aeb971377db8c3cd04ebf9f7a16
GitHub-Last-Rev: 465da88
GitHub-Pull-Request: #62611
Reviewed-on: https://go-review.googlesource.com/c/go/+/527975
Reviewed-by: qiulaidongfeng <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>

Author: callthingsoff

src/regexp/backtrack.go

@@ -91,9 +91,7 @@ func (b *bitState) reset(prog *syntax.Prog, end int, ncap int) {
 		b.visited = make([]uint32, visitedSize, maxBacktrackVector/visitedBits)
 	} else {
 		b.visited = b.visited[:visitedSize]
-		for i := range b.visited {
-			b.visited[i] = 0
-		}
+		clear(b.visited) // set to 0
 	}
 
 	if cap(b.cap) < ncap {