Update disposable/callback.md
Update disposable/callback.md

Update link to operation using version in url

from: /gems/operation/callback.html
to: /gems/operation/1.1/callback.html
trailblazer/trailblazer.github.io,trailblazer/trailblazer.github.io,trailblazer/trailblazer.github.io,trailblazer/trailblazer.github.io