Fix configuration names secret_path vs secret_file

[schildbach]

It's the other way round: Synapse requires secret_path, MAS requires secret_file.

(I think it should be changed to secret_file for both, because it's a file not a directory or tree.)

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[schildbach]

I won't sign CLAs.