remove default openai endpoint

Author: sawka

pkg/aiusechat/usechat.go

@@ -29,8 +29,6 @@ const DefaultAPI = APIType_OpenAI
 const DefaultAnthropicModel = "claude-sonnet-4-20250514"
 const DefaultAIEndpoint = "https://cfapi.waveterm.dev/api/waveai"
 const DefaultMaxTokens = 4 * 1024
-
-const DefaultOpenAIEndpoint = "https://api.openai.com/v1/responses"
 const DefaultOpenAIModel = "gpt-5-mini"
 
 var SystemPromptText = strings.Join([]string{