[swarming] remove duplicate to_proto function
[swarming] remove duplicate to_proto function

Change-Id: I3751851394a1149935db52d2d04d395e93ab321e
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2547617
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Commit-Queue: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py