Upgrading @rest-hooks/test to 6

@rest-hooks/test uses react-hooks-testing-library internally. Version 7 has a major version upgrade for this library, so the following breaking changes also apply to @rest-hooks/test@6

• 'suppressErrorOutput will now work when explicitly called, even if the RHTL_DISABLE_ERROR_FILTERING env variable has been set' (from react-hooks-testing-library)
• requires node 12 or above

@rest-hooks/test@6 Release notes