message: Switch instance type to e2-micro
  e2-micro is the new GCP Free Tier instance type.  It's also faster and
  has more RAM than the old f1-micro type.
diff: @@ -49,7 +49,7 @@ export class GcpAccount implements gcp.Account {
  private static readonly OUTLINE_PROJECT_NAME = 'Outline servers';
  private static readonly OUTLINE_FIREWALL_NAME = 'outline';
  private static readonly OUTLINE_FIREWALL_TAG = 'outline';
  - private static readonly MACHINE_SIZE = 'f1-micro';
  + private static readonly MACHINE_SIZE = 'e2-micro';
  private static readonly REQUIRED_GCP_SERVICES = ['compute.googleapis.com'];
  private readonly apiClient: gcp_api.RestApiClient;
  