Remove discontinued Conv6ations

[butyoutried]

Conv6ations archived on F-Droid with comment from author: "My patches lives in blabber.im — i am not willing to maintain this Conversations fork anymore".

Conference room also states: "Conv6ations was archived. It had mainly three changes: color, using chat.sum7.eu as server and patching a preference of ipv4 away. This patch is in blabber.im — just for color and default server name I do not need to maintain a fork".