Fix Qwen2.5 VL image grid docstring (#27033)

Signed-off-by: zitian zhao <zitian.zhao@tencentmusic.com>

vllm/model_executor/models/qwen2_5_vl.py

@@ -116,7 +116,7 @@ class Qwen2_5_VLImagePixelInputs(TensorSchema):
         - pixel_values shape: (num_patches, num_channels * patch_size *
           patch_size)
         - image_grid_thw shape: (num_images, 3) in (grid_t, grid_h, grid_w)
-          formatnum_channels * patch_size * patch_size
+          format.
     """
 
     type: Literal["pixel_values"]