[Model] Always use Transformers backend for PaliGemma and Gemma3-MM (#26715)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/models/multimodal/processing/test_common.py

@@ -222,7 +222,6 @@ def _test_processing_correctness(
 _ADD_SPECIAL_TOKENS_OVERRIDES = {
     "ovis": False,
     "ovis2_5": False,
-    "paligemma": False,
     "ultravox": False,
     "whisper": False,
 }
@@ -333,7 +332,6 @@ def _test_processing_correctness_one(
         "deepseek-ai/deepseek-vl2-tiny",
         "baidu/ERNIE-4.5-VL-28B-A3B-PT",
         "adept/fuyu-8b",
-        "google/gemma-3-4b-it",
         "google/gemma-3n-E2B-it",
         "zai-org/glm-4v-9b",
         "zai-org/GLM-4.1V-9B-Thinking",
@@ -370,8 +368,6 @@ def _test_processing_correctness_one(
         "AIDC-AI/Ovis1.6-Llama3.2-3B",
         "AIDC-AI/Ovis2-1B",
         "AIDC-AI/Ovis2.5-2B",
-        "google/paligemma-3b-mix-224",
-        "google/paligemma2-3b-ft-docci-448",
         "microsoft/Phi-3.5-vision-instruct",
         "microsoft/Phi-4-multimodal-instruct",
         "mistralai/Pixtral-12B-2409",