test(nemotron-omni-cp): switch ep8cp2 backend to TE linear + deepep dispatcher

Align the CP-enabled yaml with the non-CP cordv2 baseline:
  - linear: torch -> te
  - enable_deepep: false -> dispatcher: deepep (matches cord_v2.yaml)

Now ep8cp2 differs from non-CP cordv2 only in:
  - attn: sdpa -> te  (TE-CP path is the supported one)
  - cp_size: 1 -> 2  (the actual CP-under-test)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: HuiyingLi <willwin.lee@gmail.com>

Author: HuiyingLi

examples/vlm_finetune/nemotron_omni/nemotron_omni_v3_cord_v2_ep8cp2.yaml

@@ -30,10 +30,10 @@ model:
   backend:
     _target_: nemo_automodel.components.models.common.BackendConfig
     attn: te
-    linear: torch
+    linear: te
     rms_norm: torch_fp32
     rope_fusion: false
-    enable_deepep: false
+    dispatcher: deepep
     fake_balanced_gate: false
     enable_hf_state_dict_adapter: true