misc: Do not show arrows on some popovers

src/session/view/content/room_history/mod.rs

@@ -751,7 +751,7 @@ impl RoomHistory {
     pub fn item_context_menu(&self) -> &gtk::PopoverMenu {
         self.imp()
             .item_context_menu
-            .get_or_init(|| gtk::PopoverMenu::from_model(gio::MenuModel::NONE))
+            .get_or_init(|| gtk::PopoverMenu::builder().has_arrow(false).build())
     }
 
     pub fn item_reaction_chooser(&self) -> &ReactionChooser {

src/session/view/content/room_history/read_receipts_list/read_receipts_popover.ui

@@ -6,6 +6,7 @@
     </style>
     <property name="autohide">true</property>
     <property name="width-request">260</property>
+    <property name="has-arrow">false</property>
     <property name="child">
       <object class="GtkScrolledWindow" id="scrolled_window">
         <property name="propagate-natural-height">true</property>

src/session/view/sidebar/mod.rs

@@ -350,8 +350,12 @@ impl Sidebar {
 
     pub fn room_row_popover(&self) -> &gtk::PopoverMenu {
         let imp = self.imp();
-        imp.room_row_popover
-            .get_or_init(|| gtk::PopoverMenu::from_model(Some(&*imp.room_row_menu)))
+        imp.room_row_popover.get_or_init(|| {
+            gtk::PopoverMenu::builder()
+                .menu_model(&*imp.room_row_menu)
+                .has_arrow(false)
+                .build()
+        })
     }
 
     /// Returns the parent `Window` containing the `Sidebar`