fix(indexer): drop default [http_service] block from fly.indexer.toml
`flyctl launch --copy-config` regenerates the toml with its standard
webserver template, which adds an [http_service] pointing at a
non-existent 'app' process and trips validation.
The indexer is a background worker — long-lived outbound WebSocket to
Jetstream, no inbound HTTP — so the right answer is to remove the block
entirely and let the [processes] worker definition stand alone.
Made-with: Cursor