Use updated path to s6-svscan after alpine upgrade (#33185)

Fix #33163

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

docker/root/usr/bin/entrypoint

@@ -37,5 +37,5 @@ done
 if [ $# -gt 0 ]; then
     exec "$@"
 else
-    exec /bin/s6-svscan /etc/s6
+    exec /usr/bin/s6-svscan /etc/s6
 fi