[202012][submodule] Update swss pointer

* c3691d3 [202012][pfcwd] Convert polling interval from ms to us in LUA scripts (sonic-net#1909)
* 549c804 Mux state order change (sonic-net#1902)
* 6b0b2c4 Update acl type check logic (sonic-net#1886)

Signed-off-by: Volodymyr Samotiy <volodymyrs@nvidia.com>