Apply suggestion from @mc-nv

Author: mc-nv

tools/gen_ort_dockerfile.py

@@ -268,7 +268,7 @@ def dockerfile_for_linux(output_file):
 ARG ONNXRUNTIME_BUILD_CONFIG
 
 # TODO: Switch to release branch
-RUN git clone -b main --recursive ${ONNXRUNTIME_REPO} onnxruntime
+RUN git clone -b rel-${ONNXRUNTIME_VERSION} --recursive ${ONNXRUNTIME_REPO} onnxruntime
         """
 
     if FLAGS.onnx_tensorrt_tag != "":