feat: add gemini tool_calls finish reason

relay/common/relay_utils.go

@@ -10,8 +10,6 @@ import (
 	"strings"
 )
 
-var StopFinishReason = "stop"
-
 func GetFullRequestURL(baseURL string, requestURL string, channelType int) string {
 	fullRequestURL := fmt.Sprintf("%s%s", baseURL, requestURL)