Exclude users from all/rustaceans-connections

[apiraino]

this way we can prevent people from being auto-readded to a Zulip stream when they don't want

r? @Kobzol

(let's see if someone else wants to be added)

[rustbot]

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[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/libz-sys':
      Environments:
        ❌ Delete: copilot

[steffahn]

Some alternatives besides individually listing people here may include e. g.

• telling people to just mute the channel (unless there are significant shortcomings then still, compared to properly unsubscribing)
• general solutions¹ involving the "who can subscribe to this channel" permissions (users with this permission on a private channel can always see/preview that private channel's contents, and can subscribe or unsubscribe at will)

Footnotes

1. "general" because I don't see any strong reason not to allow users this possibility for any private channel. I'd assume we'd still - somehow - want to auto-subscribe them once when joining (and auto-unsubscribe when leaving the team) ↩