Fix failing build w/ android platform and broken mobile HCP
Fix failing build w/ android platform and broken mobile HCP

- Remove the Android platform because it fails due to the Android tools not being installed
- Leave iOS because otherwise mobile hot code push doesn't work (`/__cordova/manifest.json` is not generated if there are no mobile platforms)
- NOTE that this means HCP is broken for android-only apps! I can't think of a solution for that.

domo-lab/meteor-buildpack-horse,forwarder/meteor-buildpack-horse,spozi/meteor-buildpack-horse,dalloro/meteor-buildpack-pony,lirbank/meteor-buildpack-horse,RocketChat/heroku-buildpack-meteor,webantic/meteor-buildpack-horse,okgrow/meteor-buildpack-horse,vmtung/heroku-meteor-buildpack,tab00/prebuiltdeploy,smartphoneorchestra/heroku-buildpack-meteor-ffmpeg-lame,jad11v/meteor-buildpack-horse,AdmitHub/meteor-buildpack-horse,hexsprite/meteor-buildpack-horse,rolltapeinc/meteor-buildpack-horse