[DEMO] Scope perf-smoke matrix to Cartpole + Factory + Velocity-Flat-G1

Trim to three well-baselined demo tasks (Cartpole physx/newton, Factory
physx, G1 physx/newton) for a clean multi-row verdict table. Demo only;
not for merge.

Author: Neil4561

tools/perf_smoke_test/tasks.json

@@ -38,25 +38,6 @@
         }
       }
     },
-    {
-      "task_id": "Isaac-Repose-Cube-Shadow-Vision-Direct-v0",
-      "timeout_minutes": 20,
-      "tags": ["camera"],
-      "backends": [
-        {"physics": "physx"},
-        {"physics": "physx", "render": "newton_renderer"},
-        {"physics": "newton"},
-        {"physics": "newton", "render": "newton_renderer"}
-      ],
-      "fps_mean_floor": {
-        "L40S": {
-          "physx": 20.0,
-          "physx_newton_renderer": 0.0,
-          "newton": 0.0,
-          "newton_newton_renderer": 0.0
-        }
-      }
-    },
     {
       "task_id": "Isaac-Velocity-Flat-G1-v0",
       "timeout_minutes": 12,