chore: sort Gemini models (#8951)

api/core/model_runtime/model_providers/google/llm/_position.yaml

+- gemini-1.5-pro
+- gemini-1.5-pro-latest
+- gemini-1.5-pro-001
+- gemini-1.5-pro-002
+- gemini-1.5-pro-exp-0801
+- gemini-1.5-pro-exp-0827
+- gemini-1.5-flash
+- gemini-1.5-flash-latest
+- gemini-1.5-flash-001
+- gemini-1.5-flash-002
+- gemini-1.5-flash-exp-0827
+- gemini-1.5-flash-8b-exp-0827
+- gemini-1.5-flash-8b-exp-0924
+- gemini-pro
+- gemini-pro-vision