QA: uploads removed from MobileFrontend

As of https://gerrit.wikimedia.org/r/#/c/156523 uploading
from MF is not allowed at all.
I removed completely two steps that check for the Upload link
However, two tests that actually upload files I only removed
from the Jenkins builds.  Max mentioned that we may revisit
uploading from MF at some point, at which time these tests
would be valuable again.

Change-Id: I6da1ab4213ed56e4768d781ba4ce7eeccc862209