fix(railties): keep spring on `rails app:update`

Hello there,

I submitted this PR, to fix what I think is a bug: https://github.com/rails/rails/pull/37804
Indeed, when you run rails app:update, spring binstub --all is not run when spring is defined. Which lead to spring no longer being integrated into your binaries.

If someone could take a look, give me feedback and let me know what the next steps are, that would be great.

Cheers,
Florent.