Remove filtering by the buyable (#65)

### Description

The buyable flag is never disabled anywhere in the game, and if this flag is set to 0, the robot won’t be shown on the CRF at all—so I think we should remove it.

### Game

_No response_

### Please confirm

- [x] I am the legal owner or represent the owner of all work submitted
- [x] I consent to my submission being added to this FOSS project
- [ ] This PR used LLMs to generate some or all of the code changes

Reviewed-on: https://git.ngram.ca/OpenJam/rc-servers/pulls/65
Co-authored-by: MaxSignal <kastera58@gmail.com>
Co-committed-by: MaxSignal <kastera58@gmail.com>

rc_factory/src/arc/adapter.rs

@@ -141,9 +141,6 @@ impl crate::VehicleFactoryAdapter for ArcAdapter {
         if query.maximum_cpu < usize::MAX {
             query_builder = query_builder.filter(super::entities::robot_metadata::Column::Cpu.lte(query.maximum_cpu as u32));
         }
-        if query.buyable {
-            query_builder = query_builder.filter(super::entities::robot_metadata::Column::Buyable.ne(0));
-        }
         if !self.ignore_expiry {
             let now_str = chrono::Utc::now().to_rfc3339_opts(chrono::SecondsFormat::Secs, true).trim_end_matches('Z').to_owned();
             log::debug!("Expiry must exceed `{}`", now_str);