Remove Blender file format

[plankp]

According to the Unity cloud build site, it says Proprietary 3D files are not supported at this time. Blender files (.blend) happens to be one of the files.

Check out this site for potential solve: http://kzarczynski.com/2015/11/wanted-to-use-unity-cloud-build-but-all-my-blender-models-disappeared-solution/