message: vendor: correct the path to cargo config
  When running `cargo vendor`, users are prompted to add the configuration to their cargo config.  Unfortunately, the path named is not correct, as it's lacking the correct suffix.
diff: @@ -33,7 +33,7 @@ pub fn vendor(ws: &Workspace<'_>, opts: &VendorOptions<'_>) -> CargoResult<()> {
  if config.shell().verbosity() != Verbosity::Quiet {
  crate::drop_eprint!(
  config,
  - "To use vendored sources, add this to your .cargo/config for this project:\n\n"
  + "To use vendored sources, add this to your .cargo/config.toml for this project:\n\n"
  );
  crate::drop_print!(config, "{}", &toml::to_string(&vendor_config).unwrap());
  }
  