[sonic-utilities]: Submodule update:

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

Signed-off-by: Lawrence Lee <lawlee@microsoft.com>