Change: Remove support for ownCloud Server (OC10)

Support for ownCloud 10 servers has been removed. The client now
requires ownCloud Infinite Scale. This includes removal of OC10
authentication flows, sharing code, thumbnail API, update channels,
chunked uploads, and the legacy WebFinger fallback.

https://github.com/owncloud/client/pull/12167
https://github.com/owncloud/client/pull/12176
https://github.com/owncloud/client/pull/12198
https://github.com/owncloud/client/pull/12204
https://github.com/owncloud/client/pull/12222
https://github.com/owncloud/client/pull/12302
https://github.com/owncloud/client/pull/12429
