Fix the color on the insufficient powerlevel warning

resources/qml/MessageInput.qml

@@ -451,8 +451,9 @@ Rectangle {
             }
         }
     }
-    Text {
+    Label {
         anchors.centerIn: parent
+        color: palette.placeholderText
         text: qsTr("You don't have permission to send messages in this room")
         visible: room ? (!room.permissions.canSend(MtxEvent.TextMessage)) : false
     }