Fix deps for local docs build for Rust `1.75.0` (#2896)

- Fix docs deps build issue
(https://github.com/servo/rust-smallvec/issues/327) (Please forgive me
and LMK if there are processes I need to follow for the bump a dep here
I am not aware of).
- Fix links for `meta_contributing` docs, internal and external.
- `cargo +nightly fmt` for `/docs/...` files