Update status from Accepted to Implemented (Swift 6.3)

Author: maartene

proposals/testing/0016-test-cancellation.md

@@ -3,7 +3,7 @@
 * Proposal: [ST-0016](0016-test-cancellation.md)
 * Authors: [Jonathan Grynspan](https://github.com/grynspan)
 * Review Manager: [Maarten Engels](https://github.com/maartene)
-* Status: **Accepted**
+* Status: **Implemented (Swift 6.3)**
 * Bug: [swiftlang/swift-testing#120](https://github.com/swiftlang/swift-testing/issues/120)
 * Implementation: [swiftlang/swift-testing#1284](https://github.com/swiftlang/swift-testing/pull/1284)
 * Review: ([pitch](https://forums.swift.org/t/pitch-test-cancellation/81847)) ([review](https://forums.swift.org/t/st-0016-test-cancellation/82817)) ([acceptance](https://forums.swift.org/t/accepted-st-0016-test-cancellation/83270))