Remove obsolete comment about no-op job generator.

No-op jobs no longer exist for dummy builders that are named as mirrors
for trybots. Those builders can now appear as mirrors in a trybot config
but can't specify a parent builder, so they won't be triggered. No-op
jobs continue to exist for tester builders where for whatever reason we
do not want to run them on the branches.

Change-Id: I0a0f5ac5213ff7aef9e1c7e73730428756f3f2b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462236
Auto-Submit: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Stephen Martinis <martiniss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815310}

infra/config/main.star

@@ -132,12 +132,6 @@ branches.exec("//subprojects/webrtc/subproject.star")
 
 branches.exec("//generators/cq-builders-md.star")
 
-# TODO(https://crbug.com/819899) There are a number of noop jobs for dummy
-# builders defined due to legacy requirements that trybots mirror CI bots
-# no-op scheduler jobs are not supported by the lucicfg libraries, so this
-# generator adds in the necessary no-op jobs
-# The trybots should be update to not require no-op jobs to be triggered so that
-# the no-op jobs can be removed
 exec("//generators/scheduler-noop-jobs.star")
 exec("//generators/sort-consoles.star")