chore: GenAI Client - Update example Gemini model name in error message.

PiperOrigin-RevId: 903364953

Author: jsondai

vertexai/_genai/_evals_common.py

@@ -838,7 +838,7 @@ def _run_inference_internal(
             # Unsupported model string
             raise TypeError(
                 f"Unsupported string model name: {model}. Expecting a Gemini model"
-                " name (e.g., 'gemini-1.5-pro', 'projects/.../models/...') or a"
+                " name (e.g., 'gemini-2.5-pro', 'projects/.../models/...') or a"
                 " LiteLLM supported model name (e.g., 'openai/gpt-4o')."
                 " If using a third-party model via LiteLLM, ensure the"
                 " necessary environment variables are set (e.g., for OpenAI:"