Use TypeError for non-string input in count_vowels

strings/count_vowels.py

@@ -22,7 +22,7 @@ def count_vowels(s: str) -> int:
     1
     """
     if not isinstance(s, str):
-        raise ValueError("Input must be a string")
+        raise TypeError("Input must be a string")
 
     vowels = "aeiouAEIOU"
     return sum(1 for char in s if char in vowels)