Can't add HASURA_GRAPHQL_V1_BOOLEAN_NULL_COLLAPSE to v2

We're trying to upgrade our Hasura instance and would rather use the v1 boolean for now until we have time to migrate our queries. However, when we try to do this on the Hasura Cloud instance, we get the following error:

```
Error adding config var: {"location":"","message":"{\"location\":\"\",\"message\":\"failed to process env update for HASURA_GRAPHQL_V1_BOOLEAN_NULL_COLLAPSE failed with variable HASURA_GRAPHQL_V1_BOOLEAN_NULL_COLLAPSE can not be updated on major version 2\"}"}
```

Is this by design or an error? According to the [Upgrade Hasura v2 docs](https://hasura.io/docs/latest/graphql/core/guides/upgrade-hasura-v2.html), we should be able to do this.

Note: This also appears to work locally just not in the cloud.