Update Action Scheduler to version 3.5.4

[jonathanstegall]

Is this update related to a problem? Please describe.
It does include a big problem but I already merged the fix independently a while back. I don't think this version is likely to have a ton of impact.

Current version the plugin includes
Action Scheduler 3.5.3 (plus an extra fix from #508)

Version to be included
Action Scheduler 3.5.4

Have you tested this update? What happened?
not at all

Additional context
I'm not at MinnPost anymore so it might take me a bit!