This pull request changes weights of yolov7 model. This was required as the onnx graph of the previous yolov7 outputted detections and as well as features maps of the model. Having vector of 4 tensors would make unification of API for YOLO models problematic, thus change was required.

Weights are located in this PR #1134

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
• The PR is proposed to the proper branch
• There is a reference to the original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake