[HOTFIX] Fixing two issues with the release script.

1. The version replacement was still producing some false changes.
2. Uploads to the staging repo specifically.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #3608 from pwendell/release-script and squashes the following commits:

3c63294 [Patrick Wendell] Fixing two issues with the release script:

(cherry picked from commit 8dae26f83818ee0f5ce8e5b083625170d2e901c5)
Signed-off-by: Patrick Wendell <pwendell@gmail.com>