TimelineItem.qml: disable animation on avatars

This animation doesn't add much to the smooth display of the timeline;
worse, it started triggering a segfault with recent Qt (probably due to
a binding loop going really wrong somewhere). The code is commented out
for now but will likely be dropped entirely.

client/qml/TimelineItem.qml

@@ -238,7 +238,7 @@ Item {
                 sourceSize: Qt.size(width, -1)
 
                 AuthorInteractionArea { }
-                AnimationBehavior on height { FastNumberAnimation { } }
+                // AnimationBehavior on height { FastNumberAnimation { } }
             }
             Label {
                 id: authorLabel