fixing some things with NewVideo.qml

First I've updated the styles to fit better. Then I've moved the timer
into the NewVideo.qml item. This will help to make sure we know where
that timer is coming from.

src/qml/presenter/Library.qml

@@ -1,4 +1,4 @@
-import QtQuick 2.13
+import QtQuick 2.15
 import QtQuick.Controls 2.15 as Controls
 import QtQuick.Layouts 1.15
 import Qt.labs.platform 1.1 as Labs
@@ -82,15 +82,6 @@ Item {
                 id: newVideo
             }
 
-            Timer {
-                id: videoDLTimer
-                interval: 3000
-                running: !newVideo.sheetOpen
-                onTriggered: {
-                    newVideo.clear();
-                }
-            }
-
             Presenter.LibraryItem {
                 id: imageLibrary
                 Layout.alignment: Qt.AlignTop