Fix armstrong logic

[2007aman]

This PR improves the is_armstrong_number implementation by replacing manual loops with a more Pythonic approach.

Refactored Logic: Replaced the explicit list creation and for loop with a memory-efficient generator expression and the sum() function.

Improved Reusability: Modified the function to return a boolean value instead of printing directly, allowing it to be used as a utility in other modules.

Performance: Reduced the space complexity from O(n) to O(1) (auxiliary space) by avoiding unnecessary list storage.