fix: use correct gen_snapshot path on ios (#2695)

packages/shorebird_cli/lib/src/shorebird_artifacts.dart

@@ -128,7 +128,7 @@ class ShorebirdCachedArtifacts implements ShorebirdArtifacts {
         'artifacts',
         'engine',
         'ios-release',
-        'gen_snapshot',
+        'gen_snapshot_arm64',
       ),
     );
   }

packages/shorebird_cli/test/src/shorebird_artifacts_test.dart

@@ -119,7 +119,7 @@ void main() {
               'artifacts',
               'engine',
               'ios-release',
-              'gen_snapshot',
+              'gen_snapshot_arm64',
             ),
           ),
         );