Fix 404 error handling

[tommy-mitchell]

With the switch to ky, the HTTP status code is now on error.response.status.

[tommy-mitchell]

@sindresorhus noticed this could be break if error is not an HTTPError:

npm-user/index.js

Lines 28 to 32 in 38a7c48

	if (error.response.status === 404) {
	const notFoundError = new Error(`User \`${username}\` could not be found`, {cause: error});
	notFoundError.code = 'ERR_NO_NPM_USER';
	throw notFoundError;
	}

Should probably be error?.response?.status.

[sindresorhus]

https://github.com/sindresorhus/npm-user/releases/tag/v6.1.1