stress/sizes: Fix an off-by-one issue.

Algorithmically, a size greater than 1024 ZB could access one-past-the-end of
the sizes array.  This couldn't really happen since SIZE_MAX is less than 1024
ZB on all platforms we support (and we pick the arguments to this function to be
reasonable anyways), but it's not like there's any reason *not* to fix it,
either.

test/stress/sizes.c

@@ -17,7 +17,7 @@ do_print(const char *name, size_t sz_bytes) {
 
 	size_t ind = 0;
 	double sz = sz_bytes;
-	while (sz >= 1024 && ind < sizes_max) {
+	while (sz >= 1024 && ind < sizes_max - 1) {
 		sz /= 1024;
 		ind++;
 	}