readitlater/getpocket: Looks for login credentials under HTTPS site as well as HTTP site

The readitlater/getpocket plugin looks for getpocket credentials in Firefox's Password Manager under the site "http://getpocket.com". I have mine stored in "https://getpocket.com", however.

This pull request changes the plugin to search for credentials under both "http://getpocket.com" and "https://getpocket.com".