Fix code scanning alert #29: Incorrect conversion between integer types

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

libgo/go/net/http/pprof/pprof.go

@@ -202,7 +202,7 @@ func Symbol(w http.ResponseWriter, r *http.Request) {
 		}
 		pc, _ := strconv.ParseUint(string(word), 0, 64)
 		if pc != 0 {
-			if pc > ^uint64(0)>>1 {
+			if pc > ^uint64(uintptr(0)) {
 				fmt.Fprintf(&buf, "address out of range: %v\n", pc)
 				continue
 			}