Don't incorrectly claim to support KIO::open

Summary:
Docs for KProtocolManager::supportsOpening() states that when it
returns true, it means that the protocol supports the FileJob interface
(KIO::open). GDrive does not support this interface so this function should
return false. To make it do so, the json file needs to be amended.

Test Plan: Compiles

Reviewers: elvisangelaccio

Differential Revision: https://phabricator.kde.org/D28363