Update group & priority tags in unet model (#2961)

### Ticket

- Fixes #2960

### Problem description

- UNet tests in tt-forge-fe using two UNet implementations currently.
The goal is to determine which one mimics the [target tensorflow
implementation](https://github.com/hassanlougithub/brain-tumor-seg) and
keep only that test in red.
-
[vgg19_unet/pytorch/loader.py](https://github.com/tenstorrent/tt-forge-models/blob/main/vgg19_unet/pytorch/loader.py)
-
[unet/pytorch/loader.py](https://github.com/tenstorrent/tt-forge-models/blob/57faf96e6050915e4fc6f22454e32609479ca4b6/unet/pytorch/loader.py#L69C13-L69C63)

### What's changed

- Red tag removed from the test using
[unet/pytorch/loader.py](https://github.com/tenstorrent/tt-forge-models/blob/57faf96e6050915e4fc6f22454e32609479ca4b6/unet/pytorch/loader.py#L69C13-L69C63)
as it fails to mimic target implementation
- Added red tag to the test using
[vgg19_unet/pytorch/loader.py](https://github.com/tenstorrent/tt-forge-models/blob/main/vgg19_unet/pytorch/loader.py)
as it exactly matches the target TensorFlow implementation. for more
context refer -
tenstorrent/tt-forge-models#152 (comment)

### Checklist
- [x] New/Existing tests provide coverage for changes

Author: kamalrajkannan78

forge/test/models/pytorch/vision/unet/test_unet.py

@@ -88,8 +88,6 @@ def test_unet_torchhub_pytorch():
         model=ModelArch.UNET,
         source=Source.TORCH_HUB,
         task=Task.IMAGE_SEGMENTATION,
-        group=ModelGroup.RED,
-        priority=ModelPriority.P1,
     )
     pytest.xfail(reason="https://github.com/tenstorrent/tt-forge-fe/issues/2956")
 

forge/test/models/pytorch/vision/unet/test_vgg19_unet.py

@@ -32,6 +32,8 @@ def test_vgg19_unet():
         variant="default",
         task=Task.SEMANTIC_SEGMENTATION,
         source=Source.GITHUB,
+        group=ModelGroup.RED,
+        priority=ModelPriority.P1,
     )
     pytest.xfail(reason="https://github.com/tenstorrent/tt-forge-fe/issues/2888")