[StepPresentation] Replace spaces in urls with %20.
[StepPresentation] Replace spaces in urls with %20.

R=yiwzhang

Bug: 1182436
Recipe-Nontrivial-Roll: build
Recipe-Nontrivial-Roll: build_limited_scripts_slave
Recipe-Nontrivial-Roll: chromiumos
Change-Id: I2af73f80f5df39e7f3fbea2e71f51ce66676b411
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/recipes-py/+/2721061
Commit-Queue: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Commit-Queue: Yiwei Zhang <50b2a565e2e78c292794832469a30ce5abc9959c@google.com>
Auto-Submit: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Reviewed-by: Yiwei Zhang <50b2a565e2e78c292794832469a30ce5abc9959c@google.com>

luci/recipes-py,luci/recipes-py