dashboard: update consts

[panoel]

This PR does the following:

• removes karura from testnet watchers
• updates testnet endpoints shown on the dashboard for missed and signed VAAs in the monitor section
• testnet missing VAAs cloud function no longer alarms to slack.

[evan-gray]

a few structure things that could lead to bugs in your react code

[evan-gray]

getting close - main thing is that as doesn't make the data safe to use, it just overrides the type safety. would probably be best to get all of the backend code using the same helper coalesce that env var into the type

[evan-gray]

I think just missed one spot and maybe clean up that function name and then should be good? 🤞