fix the test issue from the pr review

tests/test_litellm/google_genai/test_google_genai_adapter.py

@@ -1091,7 +1091,7 @@ async def test_google_generate_content_with_openai():
     )
     
     # Use AsyncMock for proper async function mocking
-    with unittest.mock.patch("litellm.completion", new_callable=unittest.mock.MagicMock) as mock_completion:
+    with unittest.mock.patch("litellm.acompletion", new_callable=unittest.mock.AsyncMock) as mock_completion:
         # Set the return value directly on the MagicMock
         mock_completion.return_value = mock_response
         
@@ -1100,7 +1100,7 @@ async def test_google_generate_content_with_openai():
             contents=[
                 {"role": "user", "parts": [{"text": "Hello, world!"}]}
             ],
-            systemInstruction="You are a helpful assistant.",
+                systemInstruction={"parts": [{"text": "You are a helpful assistant."}]},
             safetySettings=[
                 {
                     "category": "HARM_CATEGORY_HATE_SPEECH",
@@ -1199,4 +1199,4 @@ async def test_agenerate_content_x_goog_api_key_header():
             assert headers.get("Content-Type") == "application/json", f"Expected Content-Type application/json, got {headers.get('Content-Type')}"
             
             print(f"✓ Test passed: x-goog-api-key header correctly set to {api_key_value}")
-            print(f"✓ All headers: {list(headers.keys())}")
+            print(f"✓ All headers: {list(headers.keys())}")