Fix greeting function type annotations

Author: Vishnu01113

greeting.py

@@ -1,7 +1,8 @@
-def greet_user(name):
+def greet_user(name: str) -> str:
     """Return a greeting for the given user."""
     return f"Hello, {name}! Welcome to our project."
 
 
 if __name__ == "__main__":
     print(greet_user("Student"))
+    print(greet_user("Alex"))