Fix skip-ci on `stable`. #129

Job	Run time
Check for 'skip-ci' label	1s
check-code	7m 31s
target-branch-check	0s
check-msrv	4m 14s
beacon-chain-tests	35m 21s
release-tests-windows	1h 8m 5s
op-pool-tests	13m 46s
debug-tests-ubuntu	12m 35s
network-tests	9m 30s
release-tests-ubuntu	50m 25s
slasher-tests	1m 0s
basic-simulator-ubuntu	14m 38s
execution-engine-integration-ubuntu	14m 36s
ef-tests-ubuntu	19m 7s
fallback-simulator-ubuntu	14m 58s
state-transition-vectors-ubuntu	3m 48s
cargo-udeps	6m 11s
cli-check	16m 11s
compile-with-beta-compiler	13m 26s
test-suite-success	0s
	5h 5m 23s

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