Delete index_en.rst

doc/v2/build_and_install/index_en.rst

-Install and Build
-=================
-
-.. _install_steps:
-
-Install Steps
-++++++++
-
-You can choose either pip or Docker to complete your install:
-
-.. toctree::
-   :maxdepth: 1
-
-   pip_install_en.rst
-   docker_install_en.rst
-
-Build from Source
------------------
-
-..  warning::
-
-    We recommend to directly install via above installation steps, you'll only need to build PaddlePaddle from source when you need a modifed binary.
-
-..  toctree::
-    :maxdepth: 1
-
-    build_from_source_en.md
-
-FAQ
-++++++++++
-
-`FAQ <http://www.paddlepaddle.org/docs/develop/documentation/zh/faq/build_and_install/index_en.html>`_