## Issue Addressed
NA
## Proposed Changes
Copied from #2083, changes the config milliseconds_per_slot to seconds_per_slot to avoid errors when slot duration is not a multiple of a second. To avoid deserializing old serialized data (with milliseconds instead of seconds) the Serialize and Deserialize derive got removed from the Spec struct (isn't currently used anyway).
This PR replaces #2083 for the purpose of fixing a merge conflict without requiring the input of @blacktemplar.
## Additional Info
NA
Co-authored-by: blacktemplar <blacktemplar@a1.net>