Update git submodules

Update git submodules

* Update docs/submodules/qtip from branch 'stable/danube'
  - Normalize all section headers

    - folder with `index.rst` for parts, using # with overline for heading
    - `*.rst` file for chapter, using * with overline for heading

    In each *.rst file, use the following token for heading

    - =, for sections
    - -, for subsections
    - ^, for subsubsections
    - ", for paragraphs

    Change-Id: I6c247c1f1e27e891d0dade099195ef521f7dbb72
    Signed-off-by: Yujun Zhang <zhang.yujunz@zte.com.cn>