Update pull_request_template.md

.github/pull_request_template.md

 # Create A Good Pull Request
 
-- [] Python code style verification
-- [] All models(TensorFLow/Caffe/ONNX/PyTorch) testing passed
-- [] Details about your pull request, releated issues
+- [ ] Python code style verification
+- [ ] All models(TensorFLow/Caffe/ONNX/PyTorch) testing passed
+- [ ] Details about your pull request, releated issues