[pre-commit.ci] auto fixes from pre-commit.com hooks

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Author: pre-commit-ci[bot]

maths/armstrong_numbers.py

@@ -19,7 +19,7 @@ def is_armstrong(number: int) -> bool:
     False
     >>> is_armstrong(25)
     False
-    
+
     References:
     - https://en.wikipedia.org/wiki/Narcissistic_number
     """