ci: set ci concurrency flag for prod images #100

Job	Run time
Build Beta Docker Image 🐳 (cstrike)	4m 39s
Build Beta Docker Image 🐳 (cstrike-legacy)	5m 6s
Build Beta Docker Image 🐳 (valve)	4m 38s
Build Beta Docker Image 🐳 (valve-legacy)	4m 47s
Build Beta Docker Image 🐳 (czero)	5m 36s
Build Beta Docker Image 🐳 (czero-legacy)	5m 43s
Build Beta Docker Image 🐳 (dmc)	4m 58s
Build Beta Docker Image 🐳 (gearbox)	5m 26s
Build Beta Docker Image 🐳 (ricochet)	4m 38s
Build Beta Docker Image 🐳 (dod)	6m 47s
Build Beta Docker Image 🐳 (tfc)	4m 56s
	57m 14s

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