fix misleading comment in strstr

the intent here is just to scan at least l bytes forward for the end
of the haystack and at least some decent minimum to avoid doing it
over and over if the needle is short, with no need to be precise. the
comment erroneously stated this as an estimate for MIN when it's
actually an estimate for MAX.

src/string/strstr.c

@@ -96,7 +96,7 @@ static char *twoway_strstr(const unsigned char *h, const unsigned char *n)
 	for (;;) {
 		/* Update incremental end-of-haystack pointer */
 		if (z-h < l) {
-			/* Fast estimate for MIN(l,63) */
+			/* Fast estimate for MAX(l,63) */
 			size_t grow = l | 63;
 			const unsigned char *z2 = memchr(z, 0, grow);
 			if (z2) {