fix: Do not warn on unused functions marked with #[export] #15688

Job	Run time
build-acvm-js	1m 35s
build-nargo	2m 1s
build-noirc-abi	1m 32s
build-noir-wasm	2m 1s
noirc_abi	9s
ACVM JS (Browser)	2s
ACVM JS (Node.js)	3s
noir_codegen	1s
Noir JS	1s
Example scripts	1s
Check external repo - ${{ matrix.project.repo }}	1s
noir_wasm	1s
Integration Tests (Node)	1s
Integration Tests (Browser)	1s
End	1s
	7m 31s

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