fix: Do not warn on unused functions marked with #[export] #15689

Job	Run time
build-noirc-abi	1m 33s
build-acvm-js	1m 38s
build-nargo	2m 20s
build-noir-wasm	3m 51s
noirc_abi	2m 15s
ACVM JS (Browser)	2m 16s
ACVM JS (Node.js)	45s
noir_codegen	1m 13s
Example scripts	12s
Noir JS	1m 12s
Check external repo - ${{ matrix.project.repo }}	0s
Integration Tests (Node)	2m 42s
noir_wasm	1m 30s
Integration Tests (Browser)	2m 7s
End	1s
	23m 35s

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