docs(power): concurrent-operations.md calls succeeded and failed as properties but they are methods

[TrickSumo]

Issue

The "Get Results" section in concurrent-operations.md accesses succeeded and failed as properties:

// As shown in docs — causes TypeScript error
const successful = results.succeeded.map(item => item.result);
const failed = results.failed.map(item => ({
  index: item.index,
  error: item.error
}));

This causes a TypeScript compile error:

Property 'map' does not exist on type '() => (BatchItem<number> & { result: number; })[]'

Root Cause

succeeded and failed are methods in the SDK, not properties:

Description of changes:

Add parentheses to call them as methods.