Ignore not existing FileCredentials instead of failing

[froth]

The update to sbt-scalafmt to 2.5.1 broke our gitlab-ci build pipelines.
This happens because we use the following config in sbt:
credentials += Credentials(Path.userHome / ".sbt" / ".credentials.gitlab")
It loads credentials from a file for local development to access maven repos hosted in a local gitlab installation.
In pipeline runs this is not necessary as access is automatically provided.
sbt itself just ignores the missing file in the pipeline and logs [warn] Credentials file /root/.sbt/.credentials.gitlab does not exist.

sbt-scalafmt instead exits with an error. This is because it uses val cred = Credentials.toDirect(x) (which throws if loading fails). I would prefer using Credentials.loadCredentials to get a similar experience as sbt itself.

I can try to create a pull request if you want.