[submodule] Advance sonic-utilities pointer

Update sonic-utilities submodule pointer to include the following:
* ee6d213f [generate_dump] Revert Revert generate_dump optimization PR's 2599, add fixes for empty /dump forder and symbolic links ([sonic-net#2645](sonic-net/sonic-utilities#2645))
* 784a15cc [vlan] Refresh dhcpv6_relay config while adding/deleting a vlan ([sonic-net#2660](sonic-net/sonic-utilities#2660))
* 7e94c5fa [GCU] protect loopback0 from deletion ([sonic-net#2638](sonic-net/sonic-utilities#2638))

Signed-off-by: vadymhlushko-mlnx <vadymh@nvidia.com>