Revert "updated installation.md for arch based distributions."
Revert "updated installation.md for arch based distributions."

This reverts commit 9e65e30ec98aba94721cfaf63e155a3755b1098c.

IntelRealSense/librealsense,IntelRealSense/librealsense,floe/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,floe/librealsense,floe/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense