services/horizon/ingest: remove the force flag on reingestion cmds

[sreuland]

What problem does your feature solve?

the force flag is incompatible with the new flushed data-flow of ingestion where we batch multiple ledgers in a single transaction, done in prior #5099

What would you like to see?

removal of force flag to avoid unintended mis-use

What alternatives are there?

[tamirms]

Actually, we can close this issue. The force flag is only incompatible when you have parallel workers and we already check for that:

https://github.com/stellar/go/blob/master/services/horizon/cmd/db.go#L398-L400