fix(relay-claude): set TopP to nil in Claude request to align with API requirements

relay/channel/claude/relay-claude.go

@@ -234,7 +234,7 @@ func RequestOpenAI2ClaudeMessage(c *gin.Context, textRequest dto.GeneralOpenAIRe
 		}
 		// TODO: 临时处理
 		// https://docs.anthropic.com/en/docs/build-with-claude/extended-thinking#important-considerations-when-using-extended-thinking
-		claudeRequest.TopP = common.GetPointer[float64](0)
+		claudeRequest.TopP = nil
 		claudeRequest.Temperature = common.GetPointer[float64](1.0)
 		if !model_setting.ShouldPreserveThinkingSuffix(textRequest.Model) {
 			claudeRequest.Model = strings.TrimSuffix(textRequest.Model, "-thinking")