fix: added `testnet: true` to `btrTestnet.ts` #758

Job	Run time
Size	5m 5s
Verify / Lint	3m 10s
Verify / Test (http, 1, 3)	1m 19s
Verify / Test (http, 2, 3)	1m 19s
Verify / Vectors	1m 20s
Verify / Test (http, 3, 3)	1m 13s
Verify / Test Environments (bun)	1m 5s
Verify / Test (webSocket, 1, 3)	1s
Verify / Test Environments (node-18)	1m 16s
Verify / Test Environments (node-20)	1m 18s
Verify / Test (webSocket, 2, 3)	1s
Verify / Test Environments (node-latest)	1m 11s
Verify / Test (webSocket, 3, 3)	1s
Verify / Test Environments (next)	2m 8s
Verify / Test Environments (sveltekit)	2m 2s
Verify / Test Environments (tsc)	1m 20s
Verify / Test Environments (vite)	2m 28s
Verify / Build	0s
Verify / Types	0s
Verify / Wagmi	0s
	26m 17s

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