Update _foundation.md

Author: fpseverino

documentation/core-libraries/_foundation.md

@@ -9,7 +9,7 @@ The Foundation framework defines a base layer of functionality that is required
 * Provide a level of OS independence, to enhance portability.
 
 
-Swift 6 unifies the implementation of [Foundation](https://developer.apple.com/documentation/foundation/) across all platforms. Foundation's modern, portable Swift implementation provides consistency across platforms, is more robust, and is open source.
+Swift 6 unifies the implementation of key [Foundation](https://developer.apple.com/documentation/foundation/) API across all platforms. Foundation's modern, portable Swift implementation provides consistency across platforms, is more robust, and is open source.
 
 If your app is particularly sensitive to binary size, you can import the `FoundationEssentials` library, which provides a more targeted subset of Foundation’s features that omits internationalization and localization data.