CheckSourceRuns: do not fail on unrecognized arguments

The old `check_X_source_runs` modules did not verify the arguments, so
we cannot start doing it now. Downgrade the hard error introduced in
commit 357e2ef429 (CheckSoureRuns: Add a unified way to check if a
source runs, 2020-09-14) via !5223 into a noisy warning.
7 files changed