Update docs remove extra returns from loss and extra args from callback

[Vaibhavdixit02]

Checklist

• [ ] Appropriate tests were added
• [ ] Any code changes were done in a way that does not break public API
• [ ] All documentation related to code changes were updated
• [ ] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [ ] Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[ChrisRackauckas]

There's another optimization error in there.

[Vaibhavdixit02]

The error now looks unrelated, it comes from the brusselator example in showcase https://buildkite.com/julialang/scimldocs/builds/5911#019238d1-6fd5-4ab1-85a3-0f43477ebbdc

[ChrisRackauckas]

The bruss part should be fixed now.

[ChrisRackauckas]

Since only that linkcheck failed, I'll just merge this.