update changelog for stable version 0.20.3 #320

Job	Run time
build (ubuntu-22.04, x86_64-unknown-linux-gnu)	5m 59s
build (windows-latest, x86_64-pc-windows-msvc)	8m 22s
build (ubuntu-22.04-arm, aarch64-unknown-linux-gnu)	8m 6s
build (windows-latest, aarch64-pc-windows-msvc)	7m 58s
	30m 25s

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