update changelog for stable version 0.20.2 #316

Job	Run time
build (windows-latest, x86_64-pc-windows-msvc)	9m 2s
build (windows-latest, aarch64-pc-windows-msvc)	10m 42s
build (ubuntu-22.04, x86_64-unknown-linux-gnu)	7m 3s
build (ubuntu-22.04-arm, aarch64-unknown-linux-gnu)	7m 44s
	34m 31s

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