[tests] use proper gemma class and config in lumina2 tests. (#10828)

use proper gemma class and config in lumina2 tests.

tests/pipelines/lumina2/test_pipeline_lumina2.py

@@ -2,7 +2,7 @@ import unittest
 
 import numpy as np
 import torch
-from transformers import AutoTokenizer, GemmaConfig, GemmaForCausalLM
+from transformers import AutoTokenizer, Gemma2Config, Gemma2Model
 
 from diffusers import (
     AutoencoderKL,
@@ -81,15 +81,16 @@ class Lumina2Text2ImgPipelinePipelineFastTests(unittest.TestCase, PipelineTester
         tokenizer = AutoTokenizer.from_pretrained("hf-internal-testing/dummy-gemma")
 
         torch.manual_seed(0)
-        config = GemmaConfig(
-            head_dim=2,
+        config = Gemma2Config(
+            head_dim=4,
             hidden_size=8,
-            intermediate_size=37,
-            num_attention_heads=4,
+            intermediate_size=8,
+            num_attention_heads=2,
             num_hidden_layers=2,
-            num_key_value_heads=4,
+            num_key_value_heads=2,
+            sliding_window=2,
         )
-        text_encoder = GemmaForCausalLM(config)
+        text_encoder = Gemma2Model(config)
 
         components = {
             "transformer": transformer.eval(),