Remove skrifa from vello's public API #1947

Job	Run time
formatting	26s
cargo check (aarch64-android)	24s
cargo check (msrv) (wasm32)	39s
cargo check (msrv) (windows-latest)	1m 26s
cargo check (msrv) (macos-latest)	35s
cargo clippy (windows-latest)	2m 28s
cargo clippy (wasm32)	1m 11s
cargo check (msrv) (ubuntu-latest)	45s
cargo clippy (macos-latest)	1m 15s
cargo doc	26s
cargo clippy (ubuntu-latest)	1m 21s
Prime LFS Cache	3s
cargo test (wasm32)	23s
typos	7s
cargo test (windows-latest)	3m 1s
cargo test (macos-latest)	1m 30s
cargo test (ubuntu-latest)	2m 58s
	18m 58s

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