Fix KV Offloading + MLA AssertionError by using num_kv_heads=1 in cpu… (#37536)

Signed-off-by: xueliangyang-oeuler <yxl546827391@gmail.com>
Co-authored-by: xueliangyang-oeuler <yxl546827391@gmail.com>

vllm/v1/kv_offload/worker/cpu_gpu.py

@@ -240,7 +240,7 @@ class CpuGpuOffloadingHandlers:
             gpu_shape = gpu_tensor.shape
             attn_backend = attn_backends[layer_name]
             test_shape = attn_backend.get_kv_cache_shape(
-                num_blocks=1234, block_size=16, num_kv_heads=8, head_size=256
+                num_blocks=1234, block_size=16, num_kv_heads=1, head_size=256
             )
 
             has_layers_dim = False