[stdlib] Define placeholder availability for SwiftStdlib 6.2

Author: lorentey

utils/availability-macros.def

@@ -37,6 +37,7 @@ SwiftStdlib 5.9:macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0
 SwiftStdlib 5.10:macOS 14.4, iOS 17.4, watchOS 10.4, tvOS 17.4, visionOS 1.1
 SwiftStdlib 6.0:macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0
 SwiftStdlib 6.1:macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, visionOS 9999
+SwiftStdlib 6.2:macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, visionOS 9999
 
 # Local Variables:
 # mode: conf-unix