Revert --image-download always flag to avoid CI getting rate limited #17668

Job	Run time
Check for 'skip-ci' label	1s
check-msrv	5m 0s
check-code	8m 40s
target-branch-check	1s
release-tests-ubuntu	21m 25s
release-tests-windows	37m 37s
network-tests	15m 0s
debug-tests-ubuntu	15m 1s
beacon-chain-tests	18m 3s
op-pool-tests	18m 51s
slasher-tests	3m 25s
state-transition-vectors-ubuntu	9m 17s
basic-simulator-ubuntu	20m 37s
cargo-udeps	7m 29s
cli-check	15m 6s
compile-with-beta-compiler	13m 29s
ef-tests-ubuntu	18m 5s
execution-engine-integration-ubuntu	13m 20s
fallback-simulator-ubuntu	18m 24s
test-suite-success	5s
	4h 18m 56s

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