config: disable SwiftLint redundant_discardable_let rule

The redundant_discardable_let rule removes 'let' from 'let _ =' assignments,
which breaks Swift 6.0+ code in result builder contexts where 'let _ =' is
required for discarding void returns.

This prevents future issues where SwiftLint auto-fixes would break compilation.

Author: coenttb

.swiftlint.yml

@@ -2,6 +2,7 @@ disabled_rules:
   - line_length
   - identifier_name
   - nesting
+  - redundant_discardable_let  # Preserve 'let _ =' in result builder contexts (required for Swift 6.0+)
 
 opt_in_rules:
   - empty_count