Hide "Download folder" setting (bug 466)

Until we re-enable the download folder moving,
simply hide the preference setting altogether
to avoid user confusion ("why is this disabled").

data/ui/desktop/gpodderpreferences.ui

@@ -459,7 +459,7 @@
                 </child>
                 <child>
                   <object class="GtkHSeparator" id="hseparator19">
-                    <property name="visible">True</property>
+                    <property name="visible">False</property>
                   </object>
                   <packing>
                     <property name="right_attach">4</property>
@@ -472,7 +472,7 @@
                 </child>
                 <child>
                   <object class="GtkLabel" id="label75">
-                    <property name="visible">True</property>
+                    <property name="visible">False</property>
                     <property name="xalign">0</property>
                     <property name="label" translatable="yes">&lt;b&gt;Download Folder&lt;/b&gt;</property>
                     <property name="use_markup">True</property>
@@ -487,7 +487,7 @@
                 </child>
                 <child>
                   <object class="GtkImage" id="image2412">
-                    <property name="visible">True</property>
+                    <property name="visible">False</property>
                     <property name="icon_name">media-floppy</property>
                     <property name="icon-size">6</property>
                   </object>
@@ -500,7 +500,7 @@
                 </child>
                 <child>
                   <object class="GtkFileChooserButton" id="chooserDownloadTo">
-                    <property name="visible">True</property>
+                    <property name="visible">False</property>
                     <property name="sensitive">False</property>
                     <property name="action">select-folder</property>
                     <property name="title" translatable="yes">Select download folder</property>