Fix BuilderConfig proto, only one BuildTarget.

Fix the BuilderConfig proto, there is only one BuildTarget per
BuilderConfig.

BUG=None
TEST=./generate.sh

Change-Id: I963c3a2cde6299bd9999953ba51311d2b70158cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/2401907
Reviewed-by: Andrew Lamb <andrewlamb@chromium.org>
Reviewed-by: Mike Nichols <mikenichols@chromium.org>
Commit-Queue: David Burger <dburger@chromium.org>
Tested-by: David Burger <dburger@chromium.org>
2 files changed