The following was added to the `ActiveJob::Callbacks`,
`ActiveModel::Callbacks` and `AbstractController:Callbacks` docs
in #29072:

> NOTE: Calling the same callback multiple times will overwrite
> previous callback definitions.

The comment refers to "calling" callbacks but seems to be about defining
callbacks, as mentioned in the PR description.

In the ActiveJob and AbstractController docs, I believe this will be
misinterpreted as referring to setting callbacks, which, as far as I can
tell, does not have such a restriction.

In the ActiveModel docs, I believe it would be slightly clearer to
replace "calling" with "defining".