pgo_rust: make mypy type checking pass

BUG=None
TEST=mypy

Change-Id: Id6d21424091ef6a97238ad374abc84675adecd45
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/4769059
Commit-Queue: Bob Haarman <inglorion@chromium.org>
Tested-by: Bob Haarman <inglorion@chromium.org>
Reviewed-by: George Burgess <gbiv@chromium.org>
1 file changed