fix: Do not merge expressions that contain output witnesses #16610

Job	Run time
yarn-lock	35s
build-nargo	22s
build-noirc-abi	23s
build-noir-wasm	22s
build-acvm-js	22s
Load critical library list	4s
ACVM JS (Browser)	1s
ACVM JS (Node.js)	1s
Example scripts	1s
Check external repo - ${{ matrix.project.repo }}	1s
noir_wasm	1s
noirc_abi	1s
Noir JS	1s
Integration Tests (Browser)	1s
Integration Tests (Node)	1s
noir_codegen	1s
End	1s
	2m 19s

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