Update .go-version
Update .go-version

Update to 1.13.4 to take advantage of security fixes.
terraform-providers/terraform-provider-google,terraform-providers/terraform-provider-google,terraform-providers/terraform-provider-google,hashicorp/terraform-provider-google,hashicorp/terraform-provider-google,terraform-providers/terraform-provider-google,terraform-providers/terraform-provider-google,hashicorp/terraform-provider-google,hashicorp/terraform-provider-google