Revert OpenHarmony support

This MR removes OpenHarmony support in Oniro with the aim of moving it to its own Eclipse project in the future.

docs/yocto-build-system/oniro-build-arch.rst

@@ -7,20 +7,6 @@
 |main_project_name| Build Architecture
 ######################################
 
-Oniro build architecture is composed of multifaceted, independent, modular, and
-reusable building blocks. In order to build OpenHarmony based images and its 
-components, meta-openharmony component serves as one of the major building blocks.
-In context of OpenHarmony, the OS essentially builds upon various components and 
-respective functionalities, and in terms of functionality, the  meta-openharmony 
-component principally helps to desolate the barrier of hardware boundaries, thus
-inevitably transcending the classical OS dichotomy. 
-
-Architecturally, the `meta-openharmony` is a bitbake layer that contains recipes
-for building OpenHarmony images and components. The meta-openharmony includes a 
-number of different repo manifest files, which you can use to fetch all repositories 
-needed for building OpenHarmony. To have a successful build image, ensure that the 
-undelying dependencies and the build procedure is followed in chronological order. 
-
 ``Oniro Project`` architecture is documented using `c4 model <https://c4model.com/>`_.
 
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