allow setting zulip stream history visibility

[marcoieni]

In #t-infra > ✔ DM groups in Zulip @ 💬 they asked me to modify a zulip stream visibility.
However, it's a private stream and I'm not part of it, so I can't.
I also don't want to log in with rust-lang-owner.

Merging this PR should set this field via the API.

Manual test

Unfortunately the dry run of github actions doesn't test zulip, because you cannot have a read-only Zulip token.

I tested this by running cargo run -- sync --services zulip print-plan locally by provisioning an API key for my account.
I verified that no streams that I'm in are modified.

I also verified that a stream I'm in would be updated when editing the file locally:

    💻 Stream History Diffs:
    📝 Updating stream history:
      Name: t-crates-io/operations
      ID: 346296
      Public history: true

I had to edit the program locally to avoid errors like:

[ERROR rust_team] failed: Id of stream 'funding/private' not found. The stream probably doesn't exist and sync-team doesn't support creating it yet. Please create the stream manually and add the rust-lang-owner user to it.

AI disclosure

I used GPT5.6-Sol with the codex harness to generate this change. I reviewed its output.

[github-actions]

Dry-run check results

[WARN  rust_team::sync] sync-team is running in dry mode, no changes will be applied.
[INFO  rust_team::sync] synchronizing crates-io
[INFO  rust_team::sync] synchronizing github
[INFO  rust_team::sync] 💻 Repo Diffs:
    📝 Editing repo 'rust-lang/rustup':
      Environments:
        ❌ Delete: copilot

[rustbot]

rust_team_data/src/v1.rs has been modified, it is used (as a git dependency) by multiple sub-projects like triagebot, the www.rust-lang.org website and others.

If you are changing the data structures, please make sure that the changes are not going to break serde deserialization (adding a field is fine; removing or renaming a field isn't).

If you must do a breaking change to the format, make sure to coordinate it with all the users of the rust_team_data crate.

[Kobzol]

While we're modifying this, could you please use destructuring here, to make it harder to forget when we add new fields?

[marcoieni]

done in 1f92a3d