Clean up `addr` in docs

[geoffromer]

Description of the bug:

#5434 removed addr patterns from the language, replacing them with ref patterns, but some design docs still use addr.

Link to documentation:

https://github.com/search?q=repo%3Acarbon-language%2Fcarbon-lang+path%3A%2F%5Edocs%5C%2Fdesign%5C%2F%2F+%22addr+self%22&type=code

https://github.com/search?q=repo%3Acarbon-language%2Fcarbon-lang+path%3A%2F%5Edocs%5C%2Fdesign%5C%2F%2F+%22%60addr%60%22&type=code

What should it say instead?

addr self: <whatever>* should be rewritten to ref self: <whatever>, and where applicable, the method body should be rewritten to reflect the type change (for example, self-> should become self.).

Note that this applies only to /docs/design. The toolchain still supports addr and not ref, but that's out of scope, and documents in /proposals are never updated to reflect changes in the language.

Any other information, logs, or outputs that you want to share?

No response

[Lucky-Malik]

I would like to work on this issue, can you please assign this to me?

[geoffromer]

See here:

To pick up a “good first issue”, check to make sure there’s no in-flight pull request on the issue, and then start working on it. We don’t assign issues to new contributors because some people have different time constraints, and we want new contributors to feel welcome to pick the issue up when it may not be making progress.

As far as I know, there's only one in-flight pull request for this issue: as a drive-by fix, #5545 is going to take care of this for docs/design/values.md.

[geoffromer]

It looks like #5389 is also cleaning up some of this, but not all of it.