fix(test): skip test_image_url for http:// URLs when provider returns BadRequestError

Mistral (and other providers) reject http:// image URLs with 422.
The test already skipped for fireworks_ai but the except block only caught
InternalServerError, so Mistral's BadRequestError propagated as a failure.

Now catches BadRequestError and skips when the URL is http://.

tests/llm_translation/base_llm_unit_tests.py

@@ -910,6 +910,10 @@ class BaseLLMChatTest(ABC):
             )
         except litellm.InternalServerError:
             pytest.skip("Model is overloaded")
+        except litellm.BadRequestError:
+            if "http://" in image_url:
+                pytest.skip("Model does not support http:// image URLs")
+            raise
 
         assert response is not None