dnn: remove obsolete "build opencv_contrib with dnn module" tutorial

modules/dnn/tutorials/tutorial_dnn_build.markdown

-Build opencv_contrib with dnn module {#tutorial_dnn_build}
-====================================
-
-Introduction
-------------
-opencv_dnn module is placed in the secondary [opencv_contrib](https://github.com/opencv/opencv_contrib) repository,
-which isn't distributed in binary form, therefore you need to build it manually.
-
-To do this you need to have installed: [CMake](http://www.cmake.org/download), git, and build system (*gcc* with *make* for Linux or *MS Visual Studio* for Windows)
-
-Steps
------
--# Make any directory, for example **opencv_root**
-
--# Clone [opencv](https://github.com/opencv/opencv) and [opencv_contrib](https://github.com/opencv/opencv_contrib) repos to the **opencv_root**.
-   You can do it in terminal like here:
-@code
-cd opencv_root
-git clone https://github.com/opencv/opencv
-git clone https://github.com/opencv/opencv_contrib
-@endcode
-
--# Run [CMake-gui] and set source and build directories:
-
-    - Set source code directory to **opencv_root**/opencv;
-
-    - Set binaries directory, for example, to **opencv_root**/build_opencv.
-      This directory will contain built libraries.
-      ![](images/build_1.png)
-
--# Configure opencv:
-       - press *Configure*;
-       - choose the preferred project generator (Makefiles for Linux, MS Visual Studio for Windows);
-       - also you can set many opencv build options, for more details see @ref tutorial_linux_install.
-         ![](images/build_2.png)
-
--# In the appeared list of build parameters find parameter `OPENCV_EXTRA_MODULES_PATH` and set it to the **opencv_root**/opencv_contrib.
-   ![](images/build_3.png)
-
--# *Configure* the project again, and set build options of dnn module:
-
-    - `BUILD_opencv_dnn` parameter must exist and be checked.
-
-    - dnn module covers waste part of [Caffe](http://caffe.berkeleyvision.org) framework functionality.
-      However, to load Caffe networks libprotobuf is required.
-      You you can uncheck `BUILD_LIBPROTOBUF_FROM_SOURCES` flag to try use protobuf installed in your system.
-      Elsewise libpotobuf will be built from opencv sources.
-
-    - You can additionally check `opencv_dnn_BUILD_TORCH_IMPORTER` parameter to build [Torch7](http://torch.ch/) importer.
-      It allows you to use networks, generated by [Torch7.nn](https://github.com/torch/nn/blob/master/README.md/) module.
-      ![](images/build_4.png)
-
--# Press *Configure* and *Generate*.
-   ![](images/build_5.png)
-
--# Build the generated project:
-    - If Makefiles generator on Unix was used, run the following in terminal:
-      @code
-      cd opencv_root/build_opencv
-      make all
-      @endcode
-    - If MS Visual Studio generator was used, then open OpenCV.sln from **opencv_root**/build_opencv folder in the Visual Studio,
-      and build it by choosing **Build** -> **Build Solution** menu or using **F7** short-cut.
-
--# Now you can build own program by using libraries were built into **opencv_root**/build_opencv/lib.
-   See the following tutorials to learn how to create a program using OpenCV:
-       - @ref tutorial_windows_install
-       - @ref tutorial_linux_gcc_cmake
\ No newline at end of file

modules/dnn/tutorials/tutorial_dnn_halide.markdown

@@ -85,8 +85,6 @@ When you build OpenCV add the following configuration flags:
 
 - `HALIDE_ROOT_DIR` - path to Halide build directory
 
-How to build OpenCV with DNN module you may find in @ref tutorial_dnn_build.
-
 ## Sample
 
 @include dnn/squeezenet_halide.cpp