Raise the minimum CMake version to 3.16 to silence the deprecation QA
warning emitted by extra-cmake-modules (Gentoo bug #964407).

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.6)
+cmake_minimum_required(VERSION 3.16)

 # The Project Name
 project(fcitx5-kkc VERSION 5.1.10)