[202012][swss][utilities] advance submodule heads (#7739)

sonic-utilities:
* 8b98d45 2021-05-25 | [show] support for show muxcable firmware version of only active banks (#1629) (HEAD -> 202012) [vdahiya12]
* afd0975 2021-05-20 | [show] add support for muxcable metrics (#1615) [vdahiya12]

sonic-swss
* 7611df5 2021-05-27 | [tunneldecaporch] Set default MTU for the overlay loopback interface (#1756) (HEAD -> 202012) [Volodymyr Samotiy]
* 22fbb5c 2021-05-27 | [202012] Resolve neighbor when nexthop does not exist (#1759) (github/202012) [Shi Su]
* ec7710c 2021-05-27 | [Bulk mode] Limit the size of bulker (#1760) [Shi Su]

Signed-off-by: Ying Xie <ying.xie@microsoft.com>