Fixed Text box demo error

modules/text/samples/textbox_demo.cpp

@@ -17,7 +17,7 @@
 #include  <iomanip>
 #include  <fstream>
 
-void textbox_draw(cv::Mat &src, std::vector<cv::Rect>  &groups,std::vector<float> &probs,std::vector<cv::String> wordList,float thres=0.6);
+void textbox_draw(cv::Mat &src, std::vector<cv::Rect>  &groups,std::vector<float> &probs,std::vector<cv::String> wordList,float thres);
 inline std::string getHelpStr(std::string progFname){
     std::stringstream out;
     out << "    Demo of text detection CNN for text detection." << std::endl;