[Doc] fixed missing "scope" parameter in Computed and For docs

[tapple]

If adding the unused and optional parameters to callbacks is not desirable, I can reduce the changes to just the ones that are actually an error, namely these commits:

1. For: d268b2c
2. Computed: 9042cd0

This would reduce the PR from 20 to 8 changed files (EDIT: done)

[alexasterisk]

A lot of these are unnecessary parameters as they are never referenced. Also, usage of these should not be publicly displayed as it may be more confusing for regular users of Fusion. If someone read scope:Computed(function(use, scope) it may not make implicit sense as scope is already defined and providing it here would overshadow it when it doesn't make any sense to do so.

There are a few swapped parameters that this PR has that do need to be changed and also the index.md on the Docs is still written for v2 so I have provided more changes to this PR. I am curious about test/Spec/State/For.spec.luau as For isn't a method but a type but is being treated as a method here. I did not change that in this PR as it didn't fit and I may just be missing an internal method.

[dphfox]

Yeah I don't plan to expose the parameters if they're not used. It makes code more confusing, and it's perfectly idiomatic to omit them if they're not used (part of the reason they're ordered the way they are is because of their usage frequency, so this is part of the API design explicitly).

[tapple]

All requested changes were made. This almost entirely was just reverting the 2 commits I expected to need to revert, so, sorry to waste your time with those. The only other changes were making sure Computed was always documented as scope:Computed

[dphfox]

No worries! I appreciate that you thought to try and help out. That's always positive :)