Use mutable reduce

Sources/Brave/Frontend/Browser/Helpers/LaunchHelper.swift

@@ -127,17 +127,18 @@ private extension FilterListStorage {
   /// Return all the blocklist types that are valid for filter lists.
   var validBlocklistTypes: Set<ContentBlockerManager.BlocklistType> {
     if filterLists.isEmpty {
-      /// If we don't have filter lists yet loaded, use the settings
-      return allFilterListSettings.reduce(Set<ContentBlockerManager.BlocklistType>()) { partialResult, setting in
-        guard let componentId = setting.componentId else { return partialResult }
-        return partialResult.union([
+      // If we don't have filter lists yet loaded, use the settings
+      return allFilterListSettings.reduce(into: Set<ContentBlockerManager.BlocklistType>(), { partialResult, setting in
+        guard let componentId = setting.componentId else { return }
+
+        partialResult.formUnion([
           .filterList(componentId: componentId, isAlwaysAggressive: setting.isAlwaysAggressive)
         ])
-      }
+      })
     } else {
-      /// If we do have filter lists yet loaded, use them as they are always the most up to date and accurate
-      return filterLists.reduce(Set<ContentBlockerManager.BlocklistType>()) { partialResult, filterList in
-        return partialResult.union([
+      // If we do have filter lists yet loaded, use them as they are always the most up to date and accurate
+      return filterLists.reduce(into: Set<ContentBlockerManager.BlocklistType>()) { partialResult, filterList in
+        partialResult.formUnion([
           .filterList(componentId: filterList.entry.componentId, isAlwaysAggressive: filterList.isAlwaysAggressive)
         ])
       }