Remove beacon files from downloader .lock whitelist after 1 downloading is done

Need to do after https://github.com/ledgerwatch/erigon/pull/10006 merged

See: 

https://github.com/ledgerwatch/erigon/pull/10006#issuecomment-2069225423 and https://github.com/ledgerwatch/erigon/pull/10006#issuecomment-2073864719
