Merge pull request #28122 from asmorkalov:as/dynamic_openmp

Dropped OPENCV_FOR_OPENMP_DYNAMIC_DISABLE environment varibale in favor of standard OMP_DYNAMIC #28122

Fixes: https://github.com/opencv/opencv/issues/25717
Replaces: https://github.com/opencv/opencv/pull/28084

### 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
- [ ] 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

doc/tutorials/introduction/env_reference/env_reference.markdown

@@ -114,7 +114,7 @@ Links:
 | OPENCV_THREAD_POOL_ACTIVE_WAIT_WORKER | num | 2000 | tune pthreads parallel_for backend |
 | OPENCV_THREAD_POOL_ACTIVE_WAIT_MAIN | num | 10000 | tune pthreads parallel_for backend |
 | OPENCV_THREAD_POOL_ACTIVE_WAIT_THREADS_LIMIT | num | 0 | tune pthreads parallel_for backend |
-| OPENCV_FOR_OPENMP_DYNAMIC_DISABLE | bool | false | use single OpenMP thread |
+| OPENCV_FOR_OPENMP_DYNAMIC_DISABLE | bool | false | Removed in 4.13.0. Use standard [OMP_DYNAMIC](https://www.openmp.org/spec-html/5.0/openmpsu116.html) instead |
 
 
 ## backends

modules/core/src/parallel.cpp

@@ -465,10 +465,6 @@ namespace {
 static inline int _initMaxThreads()
 {
     int maxThreads = omp_get_max_threads();
-    if (!utils::getConfigurationParameterBool("OPENCV_FOR_OPENMP_DYNAMIC_DISABLE", false))
-    {
-        omp_set_dynamic(1);
-    }
     return maxThreads;
 }
 static int numThreadsMax = _initMaxThreads();