toxgen: Add cohere #1618

Job	Run time
Flags (pinned) (3.7, ubuntu-22.04)	1m 36s
Flags (pinned) (3.8, ubuntu-22.04)	2m 5s
Flags (pinned) (3.9, ubuntu-22.04)	1m 12s
Flags (pinned) (3.12, ubuntu-22.04)	3m 10s
Flags (pinned) (3.13, ubuntu-22.04)	3m 26s
All pinned Flags tests passed	1s
	11m 30s

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