the `record_expected_output` script now uses the `act` utility
(https://github.com/nektos/act) to run this repo's action in a container
as github actions would.
You can now pass one argument to that, `local`, to go back to running
`github-pages` on your local ruby install. (I removed the `.ruby-version`
file since we don't *need* to record using the local env anymore, so
make sure that you're on Ruby 2.7.4)
This eliminates the inconsistency between recorded output and generated
output on actions, so we don't need to ignore any lines in `diff` anymore.
Mingzi