fix: coroutine -> coroutine function.

Author: aligheshlaghi97

docs/1. Introduction to Asynchronous Programming/index.md

@@ -38,7 +38,7 @@ The [event loop](https://docs.python.org/3/library/asyncio-eventloop.html) is th
 Coroutines have been described as ["functions whose execution you can pause"](https://en.wikipedia.org/wiki/Coroutine). <br>
 This seems confusing, but wait, we will clarify it.
 Anything in Python that can be implemented with the ```async def``` statement is a coroutine function. <br>
-Here ```func``` is a coroutine:
+Here ```func``` is a coroutine function:
 ```python
 async def func():
     pass