build: Raise the CMake policy maximum version to 4.4 This is a cherry-pick of commit 6d2054b29e0e07f0def670e2f2683cc9691cbf67 from branch 'libpng18'.

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d994e23..020489e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt

@@ -14,7 +14,7 @@
 #
 # SPDX-License-Identifier: libpng-2.0
 
-cmake_minimum_required(VERSION 3.14...4.2)
+cmake_minimum_required(VERSION 3.14...4.4)
 
 set(PNGLIB_MAJOR 1)
 set(PNGLIB_MINOR 6)