Revert "Wrap uploads in SafeUpload function that validates the absence of a previous upload."

This reverts commit 4f59461e0410f2b3b2595c64f109ba003d5c9495. It failed
on Windows to find the gsutil binary.

Change-Id: I2527854ae667af5ce5e1b6ffd601096217b3d48e
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/5000
Reviewed-by: Godofredo Contreras <godofredoc@google.com>
Commit-Queue: Christopher Fujino <fujino@google.com>