Messaging and AppDistro are available in SwiftPM (#7135)

* Messaging and AppDistro are available in SwiftPM

* s/initially/currently

Author: ryanwilson

SwiftPackageManager.md

@@ -11,7 +11,7 @@ Package Manager](https://swift.org/package-manager/) in Beta status.
 - Requires Xcode 12.
 - Analytics requires clients to add `-ObjC` linker option.
 - Analytics is only supported for iOS and cannot be used in apps that support other platforms.
-- Messaging, Performance, Firebase ML, and App Distribution are not initially available.
+- Performance and Firebase ML are not currently available.
 - watchOS support is introduced in 7.0.0 for Auth, Crashlytics, Messaging, and Storage.
 
 ## Installation