Rebuild custom namespaced Guzzle libraries to get latest changes

Was security notice for one of Guzzle libs on https://github.com/leonstafford/static-html-output/pull/190

Usually, not too big a concern for WP2Static users, as dev WP sites shouldn't be publicly accessible, but worth updating when possible.

Could also look to use Mozart/Strauss, but they don't seem to be recently maintained

(custom guzzle libs I'm refering to can be found via the `composer.json` file and finding the repos in my GH account