chore: bump platform to v1.8.26-alpha.1 #467

Job	Run time
Validate release tag	6s
Build & push container images	11m 51s
Build & push loki config image	22s
Build & push tempo config image	22s
Build & push db-init config image	21s
Build & push prometheus config image	48s
Build & push otel-collector config image	25s
	14m 15s

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