Fix "jumpy messages" regression

Caused by the commit addressing #193

include/timeline/TimelineItem.h

@@ -68,20 +68,12 @@ public:
                         this,
                         &TextLabel::adjustHeight);
                 document()->setDocumentMargin(0);
-
-                setFixedHeight(document()->size().height());
-        }
-
-        QSize sizeHint() const override
-        {
-                ensurePolished();
-                return document()->size().toSize();
         }
 
         void wheelEvent(QWheelEvent *event) override { event->ignore(); }
 
 private slots:
-        void adjustHeight(const QSizeF &size) { setFixedHeight(size.height()); }
+        void adjustHeight(const QSizeF &size) { setMinimumHeight(size.height()); }
 };
 
 class TimelineItem : public QWidget