github: fix concurrency group syntax #1016

Job	Run time
Trigger platform branch rebase	3s
Freeze MCS Code	0s
Freeze Code	17s
MCS Proof	0s
Deploy MCS manifest	0s
Proof (AARCH64, zynqmp)	12m 12s
Proof (AARCH64, 1)	2h 9m 55s
Proof (AARCH64)	2h 7m 20s
Proof (AARCH64, bcm2711)	11m 48s
Proof (ARM)	15m 20s
Proof (ARM, 1)	16m 6s
Proof (ARM_HYP, exynos5)	17m 9s
Proof (ARM_HYP, 1)	14m 23s
Proof (ARM_HYP)	2h 9m 55s
Proof (RISCV64)	1h 9m 57s
Proof (RISCV64, 1)	2h 2m 38s
Proof (X64)	12m 58s
Proof (X64, 1)	12m 48s
Deploy manifest	0s
	11h 32m 49s

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