Change type hints in infix_to_prefix_conversion.py

Author: hollowcrust

Diff for: data_structures/stacks/infix_to_prefix_conversion.py

@@ -15,7 +15,7 @@
 """
 
 
-def infix_2_postfix(infix: str) -> str:
+def infix_2_postfix(infix: list[str]) -> str:
     stack = []
     post_fix = []
     priority = {