Revert "paygen_build_lib: Add GetPaygenJson()."

This reverts commit 47dfc33970e62a29e06cff2dd7153c082925f769.

Reason for revert: The build passes, but it doesn't produce any payloads.

BUG=chromium:747211
TEST=None

Original change's description:
> paygen_build_lib: Add GetPaygenJson().
>
> We are replacing all paygen config files with the new paygen.json.
>
> This CL adds logic to fetch/parse the new file, and uses it to replace
> boards.json.
>
> BUG=chromium:735191
> TEST=Unittests
>
> Change-Id: I3e0d91295a9c18ea427c72772433792a7d7ab406
> Reviewed-on: https://chromium-review.googlesource.com/557360
> Commit-Ready: Don Garrett <dgarrett@chromium.org>
> Tested-by: Don Garrett <dgarrett@chromium.org>
> Reviewed-by: Don Garrett <dgarrett@chromium.org>

Bug: chromium:735191
Change-Id: I5ba892664c38e1cbfe6888f6ff25352ea9a42913
Reviewed-on: https://chromium-review.googlesource.com/580471
Commit-Ready: Wu-Cheng Li <wuchengli@chromium.org>
Tested-by: Wu-Cheng Li <wuchengli@chromium.org>
Reviewed-by: Wu-Cheng Li <wuchengli@chromium.org>
(cherry picked from commit 1d72eae1a0a5175f6a29d90b91c2ff261b4d217f)
Reviewed-on: https://chromium-review.googlesource.com/588348
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
Commit-Queue: Bernie Thompson <bhthompson@chromium.org>
Tested-by: Bernie Thompson <bhthompson@chromium.org>
(cherry picked from commit ee5ea4bc6fc71fa82b291da0a6e50de773891103)
Reviewed-on: https://chromium-review.googlesource.com/590147
4 files changed