Apply suggestion from @ktoso

Author: ktoso

proposals/NNNN-runtime-demangle.md

@@ -4,7 +4,7 @@
 * Authors: [Konrad'ktoso'Malawski](https://github.com/ktoso), [Alejandro Alonso](https://github.com/Azoy)
 * Review Manager: TODO
 * Status: TODO
-* Implementation: 
+* Implementation: [PR #84788](https://github.com/swiftlang/swift/pull/84788)
 * Review: 
     * Previous [pitch](https://forums.swift.org/t/demangle-function/25416/16)