chatview: remove conversation loading animation

The conversation loading animation doesn't really improve UX, yet it is a perf issue.

Also, it looks ugly. We should get rid of it.

mentioned in issue #812 (closed)

Will be fixed in https://gerrit-ring.savoirfairelinux.com/c/ring-client-gnome/+/9715

mentioned in commit f9bb72ba

closed

changed milestone to %Gnome 2018.07.15

added ui/ux label