Update count_vowels.md

snippets/count_vowels.md

@@ -12,7 +12,7 @@ def count_vowels(str):
     return len(re.findall(r'[aeiou]', str, re.IGNORECASE))
 ```
 
-```python
+``` python
 count_vowels('foobar') # 3
 count_vowels('gym') # 0
 ```