fix(ci): Limit parallel jobs launched by the crates workflow #54

Job	Run time
Generate crates matrix	12s
Check crates matrix	3s
Build tower-batch-control crate	42s
Build tower-fallback crate	21s
Build zebra-chain crate	3m 28s
Build zebra-consensus crate	16m 45s
Build zebra-network crate	3m 4s
Build zebra-node-services crate	3m 2s
Build zebra-rpc crate	18m 30s
Build zebra-script crate	2m 34s
Build zebra-state crate	12m 48s
Build zebra-test crate	1m 40s
Build zebra-utils crate	14m 42s
Build zebrad crate	20m 8s
Open or update issues for building crates individually failures	0s
	1h 37m 59s

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