Cleanup ci.yml docs that referenced old code. (#15624)

Spotted these while debugging
#15623

skip-ci: comment-only change

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ name: CI
 # https://github.com/actions/runner/issues/1182
 # Neither does it have any contexts that are available everywhere. The
 # top-level `env` field is available in many places, but not all. We already
-# have a "should-run" job that every other job depends on, so we leverage that
+# have a "setup" job that every other job depends on, so we leverage that
 # for variables that every other job can use, since that *is* available in all
 # sub-fields of the job.
 # See https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability
@@ -25,15 +25,6 @@ name: CI
 # Runner label ordering:
 # - self-hosted always has to be listed first in a runs-on block:
 # https://docs.github.com/en/actions/hosting-your-own-runners/using-self-hosted-runners-in-a-workflow
-#
-# Pseudo-ternary hack:
-# - We have to do a weird hack to get a pseudo-ternary operator. See
-# https://github.com/actions/runner/issues/409, hence patterns like:
-# `github.event_name == 'pull_request' && 'presubmit' || 'postsubmit'`
-# to mean `'presubmit' if github.event_name == 'pull_request' else 'postsubmit'`
-# Note that this only works if the true branch value is truthy. If it is falsey
-# then we would always get the false branch condition (`p && false` is always
-# false).
 
 on:
   workflow_dispatch: