.azurepipelines: Add SignedCapsulePkg to CI

.azurepipelines: Add SignedCapsulePkg to CI

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=4050

Adds SignedCapsulePkg to the "OTHER" CI matrix job so it is built
in edk2 CI.

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Jian J Wang <jian.j.wang@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>