Merge pull request #29298 from Kumataro:remove_duplicated_bib

doc: remove duplicated bib #29298

### Pull Request Readiness Checklist

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

- [x] I agree to contribute to the project under Apache 2 License.
- [x] 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
- [x] The PR is proposed to the proper branch
- [x] 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

modules/objdetect/doc/objdetect.bib

@@ -11,15 +11,6 @@
   url = {http://www.sciencedirect.com/science/article/pii/S0031320314000235}
 }
 
-@inproceedings{wang2016iros,
-  author = {John Wang and Edwin Olson},
-  title = {{AprilTag} 2: Efficient and robust fiducial detection},
-  booktitle = {Proceedings of the {IEEE/RSJ} International Conference on Intelligent Robots and Systems {(IROS)}},
-  year = {2016},
-  month = {October},
-  url = {https://april.eecs.umich.edu/pdfs/wang2016iros.pdf}
-}
-
 @mastersthesis{Xiangmin2015research,
   title={Research on Barcode Recognition Technology In a Complex Background},
   author={Xiangmin, Wang},