EmulatorPkg/.azurepipelines: Enable EDK II CI for stable/* branches

EmulatorPkg/.azurepipelines: Enable EDK II CI for stable/* branches

https://bugzilla.tianocore.org/show_bug.cgi?id=3130

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Andrew Fish <afish@apple.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Acked-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>