[tests] remove TF tests (uses of require_tf) (#38944)

* remove uses of require_tf

* remove redundant import guards

* this class has no tests

* nits

* del tf rng comment

tests/test_image_transforms.py

@@ -17,16 +17,13 @@ import unittest
 import numpy as np
 from parameterized import parameterized
 
-from transformers.testing_utils import require_flax, require_tf, require_torch, require_vision
-from transformers.utils.import_utils import is_flax_available, is_tf_available, is_torch_available, is_vision_available
+from transformers.testing_utils import require_flax, require_torch, require_vision
+from transformers.utils.import_utils import is_flax_available, is_torch_available, is_vision_available
 
 
 if is_torch_available():
     import torch
 
-if is_tf_available():
-    import tensorflow as tf
-
 if is_flax_available():
     import jax
 
@@ -122,20 +119,6 @@ class ImageTransformsTester(unittest.TestCase):
         self.assertTrue(np_img.min() == 0)
         self.assertTrue(np_img.max() == 1)
 
-    @require_tf
-    def test_to_pil_image_from_tensorflow(self):
-        # channels_first
-        image = tf.random.uniform((3, 4, 5))
-        pil_image = to_pil_image(image)
-        self.assertIsInstance(pil_image, PIL.Image.Image)
-        self.assertEqual(pil_image.size, (5, 4))
-
-        # channels_last
-        image = tf.random.uniform((4, 5, 3))
-        pil_image = to_pil_image(image)
-        self.assertIsInstance(pil_image, PIL.Image.Image)
-        self.assertEqual(pil_image.size, (5, 4))
-
     @require_torch
     def test_to_pil_image_from_torch(self):
         # channels first