retention_sweep: fix stray indent on biometric_collection field

Cosmetic — the field was added correctly during the BiometricCollection
substrate landing (commit f1fa6e4) but a batch sed left it misindented.
Tests still pass (8/8); only the formatting was off.

crates/catalogd/src/bin/retention_sweep.rs

@@ -304,6 +304,7 @@ mod tests {
             safe_views: vec![],
             audit_log_path: String::new(),
             audit_log_chain_root: String::new(),
+            biometric_collection: None,
         }
     }