Add gemma3 tests

Author: simondanielsson

tests/exporters/onnx/utils_tests.py

@@ -103,6 +103,7 @@
     },
     "flaubert": "hf-internal-testing/tiny-random-flaubert",
     "gemma": "fxmarty/tiny-random-GemmaForCausalLM",
+    "gemma3": "hf-internal-testing/tiny-random-Gemma3ForConditionalGeneration",
     "glpn": "hf-internal-testing/tiny-random-GLPNModel",
     "gpt2": "hf-internal-testing/tiny-random-gpt2",
     "gpt_bigcode": "hf-internal-testing/tiny-random-GPTBigCodeModel",