CI: use GitHub native concurrency to cancel workflows #1737

Job	Run time
Extract tasks from matrix	4s
check-migrations (polkadot, polkadot-runtime, relay/polkadot, wss://polkadot-try-runtime-node.par...	22m 18s
check-migrations (kusama, staging-kusama-runtime, relay/kusama, wss://kusama-try-runtime-node.par...	14m 54s
check-migrations (asset-hub-kusama, asset-hub-kusama-runtime, system-parachains/asset-hubs/asset-...	15m 9s
check-migrations (asset-hub-polkadot, asset-hub-polkadot-runtime, system-parachains/asset-hubs/as...	34m 14s
check-migrations (bridge-hub-kusama, bridge-hub-kusama-runtime, system-parachains/bridge-hubs/bri...	10m 21s
check-migrations (bridge-hub-polkadot, bridge-hub-polkadot-runtime, system-parachains/bridge-hubs...	17m 3s
check-migrations (collectives-polkadot, collectives-polkadot-runtime, system-parachains/collectiv...	9m 50s
check-migrations (coretime-kusama, coretime-kusama-runtime, system-parachains/coretime/coretime-k...	9m 53s
check-migrations (encointer-kusama, encointer-kusama-runtime, system-parachains/encointer, wss://...	10m 9s
All migrations passed	1s
	2h 23m 56s

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