[ffigen] Prepare to publish ffigen 20.1.0 (#2801)

Author: liamappelbe

pkgs/ffigen/pubspec.yaml

@@ -3,7 +3,7 @@
 # BSD-style license that can be found in the LICENSE file.
 
 name: ffigen
-version: 20.1.0-dev
+version: 20.1.0
 description: >
   Generator for FFI bindings, using LibClang to parse C, Objective-C, and Swift
   files.

pkgs/objective_c/pubspec.yaml

@@ -4,7 +4,7 @@
 
 name: objective_c
 description: 'A library to access Objective C from Flutter that acts as a support library for package:ffigen.'
-version: 9.1.0-dev
+version: 9.1.0
 repository: https://github.com/dart-lang/native/tree/main/pkgs/objective_c
 issue_tracker: https://github.com/dart-lang/native/issues?q=is%3Aissue+is%3Aopen+label%3Apackage%3Aobjective_c