Fix build with cmake-4.

--- a/CMakeLists.txt	2016-02-18 11:13:58.000000000 +0100
+++ b/CMakeLists.txt	2025-04-01 23:01:30.907019192 +0200
@@ -1,5 +1,5 @@
+cmake_minimum_required(VERSION 3.5)
 project(dbusmenu-qt)
-cmake_minimum_required(VERSION 2.8.11)
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/modules")
 
 # Build options