[config] Delete platform_version.json This is no longer the source of truth, and is replaced by version_history.json. Change-Id: I5b7e1ed02b72ca753f793322a6e96f46046d9dc8 Reviewed-on: https://fuchsia-review.googlesource.com/c/infra/roller-tests/integration/+/885574 Commit-Queue: Anthony Fandrianto <atyfto@google.com> Reviewed-by: Danielle Kay <danikay@google.com>