build_report: fix typo "EC_CONTAINER" -> "EC_FIRMWARE"

The proto from build-api says ec_firmware, and for consistency make sure
we're using that name here too.

BUG=b:210012685
TEST=./generate.sh

Change-Id: I11f51ae7387ba7ed471fb8db43b5fb821d8563e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/3351758
Reviewed-by: George Engelbrecht <engeg@google.com>
Commit-Queue: Benjamin Shai <bshai@google.com>
3 files changed