docs: Fix dead links

[beninato8]

What was changed

I updated some dead links in comments. I found links that would 404, then searched the docs for the closest equivalent, checking the Internet Archive Wayback Machine first.

Why?

I wanted to see the actual docs that https://docs.temporal.io/concepts/what-is-continue-as-new/ pointed to. When I went to fix it, I saw other https://docs.temporal.io/concepts/* links, and updated those as well.

Checklist

1. Closes [Bug] Dead Links in Docs #2018

2. How was this tested:

I doubt docs changes would break anything, but I set up the local environment

$ git submodule update --init --recursive
$ brew install protobuf
$ brew install rust
$ pnpm install
$ pnpm build
$ pnpm lint

And everything seemed to pass

3. Any docs updates needed?

This was just a doc comment update.

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[chris-olszewski]

Please apply my one suggestion and then this looks good to merge.

[beninato8]

thanks for catching that one @chris-olszewski!