Don't push to til-db with my username

[simonw]

These automated commits are credited to me and I don't want them to be:

https://github.com/simonw/til-db/commit/b7fa037e9968a298212b2afb1f0aaa3300562303

[simonw]

That first attempt didn't work. I'm going to try this:

--author="README-bot <actions@users.noreply.github.com>"

[simonw]

That fixed it: https://github.com/simonw/til-db/commit/6281e9d879f6bcf45806dcadb08192a7e2e8d08f