Update src/items/functions.md

Co-Authored-By: Mazdak Farrokhzad <[email protected]>

Author: nikomatsakis

src/items/functions.md

@@ -252,7 +252,7 @@ For more information on the effect of async, see [`async` blocks][async-blocks].
 
 It is legal to declare a function that is both async and unsafe. The
 resulting function is unsafe to call and (like any async function)
-returns a future. This future is just an ordinary future and thus the
+returns a future. This future is just an ordinary future and thus an
 `unsafe` context is not required to "await" it:
 
 ```rust,edition2018