[sonic-utilities]: Submodule update: (#11957)

Include following commits:
```
839625d Replace cmp in acl_loader with operator.eq (#2328)
af245ad [route_check]: Ignore standalone tunnel routes (#2332)
c9aa65c Revert "[DHCPv6] [202012] Update the dhcpv6_relay config/show cli (#2271)" (#2336)
6b9cdc9 Made changes to only allow a valid IPv4 or Ipv6 string for dhcp cli (#2296)
```