[build] Fix `sources` references in swarming.yaml.
[build] Fix `sources` references in swarming.yaml.

Looks like I forgot to "rebase" them after moving
swarming.yaml from infra.git, since they still refer to
`luci` directory (it is where luci-py is in infra.git solution).

R=40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org

Change-Id: I46c96e13b94fd1abfbd46fbe8ff9758a92ce444f
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/3309491
Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Commit-Queue: Vadim Shtayura <9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org>

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