depends: expat 2.7.3

Remove the patch, as expat has bumped it's minimum to 3.15.
Remove the lto related workaround. I haven't seen issues with CMakes
TestBigEndian.

depends/patches/expat/cmake_minimum.patch

@@ -1,13 +0,0 @@
-build: set minimum required CMake to 3.16
-
---- a/CMakeLists.txt
-+++ b/CMakeLists.txt
-@@ -33,7 +33,7 @@
- # Unlike most of Expat,
- # this file is copyrighted under the BSD-license for buildsystem files of KDE.
- 
--cmake_minimum_required(VERSION 3.1.3)
-+cmake_minimum_required(VERSION 3.16)
- 
- # This allows controlling documented build time switches
- # when Expat is pulled in using the add_subdirectory function, e.g.