test: stabilize scheduler-k3s cnb bats tests

Drop the assertion that the web deployment has no command since the python buildpack auto-emits a web Procfile entry, which correctly routes through launcher just like docker-local. Shorten the cron command fixture so the base36-encoded cron-id stays under the 63-byte kubernetes label limit, and relax the `dokku run` and `dokku cron:run` output assertions to `assert_output_contains` so they tolerate the leading blank line emitted on k3s.

tests/unit/builder-pack.bats

@@ -216,7 +216,7 @@ teardown() {
   echo "output: $output"
   echo "status: $status"
   assert_success
-  assert_output "['task.py', 'some', 'cron', 'task']"
+  assert_output "['task.py']"
 }
 
 @test "(builder-pack) cron:run with Procfile reference" {