fix: refuse to start sequencer without a prover #5493

Job	Run time
setup / start-builder	4s
setup / setup	11s
yarn-project-formatting	3m 42s
build	4m 36s
yarn-project-test	3m 5s
bb-native-tests	13s
bb-bench-binaries	14s
setup-bench / start-builder	1m 3s
setup-bench / setup	20s
bb-bench	13s
e2e (e2e-browser)	1m 23s
e2e (e2e-docs-examples)	56s
e2e (e2e-sandbox-example)	1m 28s
e2e (e2e-tests)	11m 38s
e2e (flakey-e2e-tests)	4m 32s
e2e (guides-dapp-testing)	2m 54s
e2e (guides-writing-an-account-contract)	1m 2s
e2e (integration-l1-publisher)	1m 53s
e2e (pxe)	41s
e2e (uniswap-trade-on-l1-from-l2)	5m 55s
merge-check	1s
notify	0s
	46m 4s

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