cargo deny mutliple-fields ban

[clux]

using https://embarkstudios.github.io/cargo-deny/checks/bans/cfg.html#the-multiple-versions-field-optional
to try to prevent issues like #709 in the future

i had issues originally, but deleted my local Cargo.lock and on a rebuild all the duplicates had gone away.

will add and remove a duplicate dependency here to ensure that this setup works.

(there are ways to temporarily whitelist from the duplicate ban list, so this shouldn't be a big inconvenience)

[clux]

Test failed as it does locally:

error[B004]: found 2 duplicate entries for crate 'tungstenite'
    ┌─ /github/workspace/Cargo.lock:220:1
    │  
220 │ ╭ tungstenite 0.13.0 registry+https://github.com/rust-lang/crates.io-index
221 │ │ tungstenite 0.14.0 registry+https://github.com/rust-lang/crates.io-index
    │ ╰────────────────────────────────────────────────────────────────────────^ lock entries

[kazk]

There's a warning

warning[S006]: allowed 'github.com' organization  was not encountered
   ┌─ /github/workspace/deny.toml:64:11
   │
64 │ github = ["kube-rs"]
   │           ^^^^^^^^^ no crate source fell under this organization

Is this necessary for something?
https://github.com/kube-rs/kube-rs/blob/519cc7b6332b059cf0c487d81f6d32e5579272a7/deny.toml#L63-L64

[clux]

Is this necessary for something?

Technically no. i think Lars put it there as a convenience to allow things in a big org with private repos, but we don't have that stuff. I'll remove it.

[clux]

Warning gone. Merging.