Update src/items/functions.md

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

Author: gnzlbg

src/items/functions.md

@@ -120,7 +120,8 @@ An extern function _declaration_ via an [external block] can be used to
 provide an item for these functions that can be called by Rust code without
 providing their definition. 
 
-The default ABI of Rust functions like `fn foo() {}` is `"Rust"`. While we
+When `"extern" Abi?*` is omitted from `FunctionQualifiers`, the ABI `"Rust"` is assigned.
+For example:
 abbreviate the type of Rust functions like `foo` as `fn()`, this is actually a 
 synonym for `extern "Rust" fn()`. That is, this: