Remove empty Additional Resources and Exercises fields from tutorials #26002
### Pull Request Readiness Checklist
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- [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
This PR is in response to issue [26001](https://github.com/opencv/opencv/issues/26001)
This pull request addresses the issue of empty "Additional Resources" and "Exercises" fields in several OpenCV-Python tutorials. The empty sections have been removed to improve the clarity and consistency of the documentation.
Add initialisations to make clear what values actually have to be passed.
Moreover, in accordance with 383559c228/modules/flann/include/opencv2/flann/defines.h (L68), I believe `FLANN_INDEX_KDTREE` was being initialised wrongly in the code examples, 1 should be correct, whereas 0 is `FLANN_INDEX_LINEAR`.
