Disable pre-release/update notifications through an environment variable

I want to be able to immediately "opt-out" ([as it's called in 1.1.0](https://github.com/hasura/graphql-engine/releases/tag/v1.1.0)) from pre-release notifications, as well as any upgrade notification, through an environment variable similar to `HASURA_GRAPHQL_ENABLE_TELEMETRY`. Basically I don't want to see the popups in the console.

[I don't think one exists](https://hasura.io/docs/1.0/graphql/manual/deployment/graphql-engine-flags/reference.html).