chore(XML): #4477: Upgrade bundled libexpat to 2.6.1 #35

Job	Run time
mkrelease	22s
mkrelease_win	39s
windows-2022-msvc-cmake-mkrelease-all	15m 31s
windows-2022-msvc-buildwin-x64-mkrelease	17m 0s
windows-2022-msvc-cmake-mkrelease	12m 34s
windows-2022-msvc-buildwin-x64-mkrelease-all	26m 27s
linux-gcc-make-mkrelease	7m 25s
linux-gcc-cmake-mkrelease	5m 28s
linux-gcc-make-mkrelease-all	13m 9s
linux-gcc-cmake-mkrelease-all	9m 11s
	1h 47m 46s

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