Fixed ragdoll panel being available in Animation Editor when PhysX gem is enabled. (#3985)

Following the same approach as cloth plugin, which is to ask if the system component of the gem is available (in this case PhysX::SystemComponent).

Fixes #2540

Signed-off-by: moraaar moraaar@amazon.com

Gems/EMotionFX/Code/Tests/UI/CanAddToSimulatedObject.cpp

@@ -41,6 +41,7 @@ namespace EMotionFX
             AZ::SerializeContext* serializeContext = nullptr;
             AZ::ComponentApplicationBus::BroadcastResult(serializeContext, &AZ::ComponentApplicationBus::Events::GetSerializeContext);
 
+            Physics::MockPhysicsSystem::Reflect(serializeContext); // Required by Ragdoll plugin to fake PhysX Gem is available
             D6JointLimitConfiguration::Reflect(serializeContext);
 
             SetupPluginWindows();