fix casing of section title

Author: alexandersandberg

_posts/2023-08-29-swift-5.9-released.md

@@ -16,7 +16,7 @@ Thank you to everyone in the Swift community who made this release possible. You
 
 If you’re new to Swift, [The Swift Programming Language](https://docs.swift.org/swift-book/) is the official Swift guide and has been updated for version 5.9. The Swift community maintains a number of [translations](https://www.swift.org/documentation/#translations).
 
-## Language and Standard library
+## Language and Standard Library
 
 Swift 5.9 tackles three long-desired features that allow you to express things you couldn't easily do before.