chore: default to using bn254 in `noirc_frontend` #7470

Job	Run time
build-acvm-js	1m 26s
build-nargo	2m 27s
build-noirc-abi	1m 59s
build-noir-wasm	3m 46s
ACVM JS (Node.js)	36s
ACVM JS (Browser)	1m 9s
noirc_abi	1m 26s
noir-js-backend-barretenberg	53s
Noir JS	1m 32s
Example scripts	17s
noir_codegen	1m 4s
noir_wasm	2m 3s
Integration Tests (Browser)	1m 49s
Integration Tests (Node)	1m 55s
End	1s
	22m 23s

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