Missing epoch table entries when using bootstrap > prune path

[rdlrt]

Versions
The db-sync version (eg cardano-db-sync --version): 13.6.0.4
PostgreSQL version: 17.2

Problem Report
When we start dbsync using tx_out > bootstrap option, the epoch table is left empty until latest epoch - we do get a record added for the latest epoch, but nothing prior. Subsequently when we switch to prune option, there is no back-fill for previous epochs. If this is an expected state, /doc/configuration.md should be updated to note the same.