[CHERRY-PICK] SecurityPkg: Update libspdm submodule to use GitLab cmo…

…cka repo

As noted in DMTF/libspdm#2707, the cmocka
submodule on cryptomilk is unreliable and impacting downstream
consumer builds of SecurityPkg. This is considered a regression in
that pre-existing workflows that clone and recursively initialize
the repo are now broken.

The cmocka host was switched to a more reliable gitlab host in
DMTF/libspdm#2710. This change updates the
submodule in edk2 to use that commit so edk2 users are not blocked
by cryptomilk.org service issues.

Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>