[sonic-utilities] Update submodule (#6107)

* src/sonic-utilities 6fabbed...3749f5e (7):
  > [config vlan] Stop, reset-failed, then start dhcp_relay service (#1269)
  > [show] Break some groups out into their own modules (#1259)
  > Convert the output of 'arp -n' from bytes to str. (#1279)
  > Fixing python porting errors in fdbshow, natshow and nbrshow (#1280)
  > [pfcwd] Use floor division in Python3 (#1277)
  > Modify fast-reboot script to use teamd service script (#1251)
  > Add `show reboot-cause history` cli (#1210)