PERF-15 · Remove dead $scan->region read in RulesEngine::getScanner()

[kiwifellows]

Part of #63.

Problem

RulesEngine::getScanner() (app/app/Services/RulesEngine/RulesEngine.php:219) reads:

$region = $scan->region ?? 'us-east-1';

The scans table has no region column, so this always evaluates to 'us-east-1'. It works by accident, because GenericAwsScanner takes the real region per call instead.

Change

Remove the dead read. Confirm S3Scanner and IamScanner do not depend on the constructor region before deleting.

Priority: P3 — tidy-up