check build verification for templates are unstable

[jcollins-g]

e.g. https://github.com/dart-lang/dartdoc/pull/2750/checks?check_run_id=3374650937

[jcollins-g]

Yeah, not sure what's going on here and can't reproduce it locally, so just commenting out that file check until we have time to dig in.