Hari this warning doesn't actually come from the extension. It comes from flarum/core, which itself gets it because of Laravel. In general any Composer warning that doesn't directly references an extension name or Flarum itself can be ignored because they are targeted at the authors of the software.
Composer repeats all warnings every time you install/update packages, even if it doesn't belong to the current extension (technically, Flarum is always listed as a dependency of an extension so that's why it shows up)
As long as there are no other errors in the Composer output, you should be good to go.
