fix(core): disable concurrency for package subtasks (backport of #4276)

The inner package subtask list (copy-files, prepare-native-dependencies,
finalize-package) was unintentionally inheriting "concurrent": true from
the list of targets a couple of levels up. As a result all three subtasks
appear to start simultaneously in CI logs even though the underlying work
in @electron/packager runs sequentially. Set concurrent: false on that
inner list so the subtasks render sequentially.

Co-authored-by: Ryan Fitzgerald <rwfitzge@gmail.com>

Author: claude

packages/api/core/src/api/package.ts

@@ -581,6 +581,7 @@ export const listrPackage = (
                                     },
                                   ],
                                   {
+                                    concurrent: false,
                                     rendererOptions: {
                                       collapseSubtasks: true,
                                       collapseErrors: false,