strings: fix nonexistent path in comment

There is a part in the comment that points to a non-existent file.
It seems to have been overlooked in following PR.
https://go-review.googlesource.com/c/go/+/98518/

Change-Id: I21dbfbd270c654d5cd7fa88d114a356862612d90
Reviewed-on: https://go-review.googlesource.com/c/go/+/210298
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/strings/strings.go b/src/strings/strings.go
index 869cdcd..69f51b6 100644
--- a/src/strings/strings.go
+++ b/src/strings/strings.go
@@ -1094,7 +1094,7 @@
 		i++
 		fails++
 		if fails >= 4+i>>4 && i < t {
-			// See comment in ../bytes/bytes_generic.go.
+			// See comment in ../bytes/bytes.go.
 			j := indexRabinKarp(s[i:], substr)
 			if j < 0 {
 				return -1