Remove some duplicate buttons from the room sidebar

The favorites action doesn't really deserve space here IMO, and that's a
pretty list-specific action you're more likely to do elsewhere.

For the Pinned Messages action that can be opened at the top on desktop,
but we still need it on mobile. So now it's selectively hidden based on
that.

src/roominfo/RoomInformation.qml

@@ -103,19 +103,6 @@ QQC2.ScrollView {
                 Layout.fillWidth: true
             }
 
-            Delegates.RoundedItemDelegate {
-                id: favouriteButton
-                visible: !root.room.isSpace
-                icon.name: root.room && root.room.isFavourite ? "rating" : "rating-unrated"
-                text: root.room && root.room.isFavourite ? i18nc("@action:button", "Remove from Favorites") : i18nc("@action:button", "Add to Favorites")
-
-                onClicked: root.room.isFavourite ? root.room.removeTag("m.favourite") : root.room.addTag("m.favourite", 1.0)
-
-                activeFocusOnTab: true
-
-                Layout.fillWidth: true
-            }
-
             Delegates.RoundedItemDelegate {
                 id: widgetsButton
                 visible: !root.room.isSpace
@@ -150,7 +137,8 @@ QQC2.ScrollView {
 
             Delegates.RoundedItemDelegate {
                 id: pinnedMessagesButton
-                visible: !root.room.isSpace
+                // On mobile the pinned message at the top is hidden, so we need this button in that case.
+                visible: !root.room.isSpace && Kirigami.Settings.isMobile
                 icon.name: "pin-symbolic"
                 text: i18nc("@action:button", "Pinned Messages")
                 activeFocusOnTab: true