Add changelog for 0.20.2 #5688

Job	Run time
build_windows (3.10)	38m 57s
build_linux (3.10)	36m 46s
build_linux (3.9)	36m 14s
build_linux (3.11)	37m 31s
build_windows (3.9)	41m 26s
build_windows (3.11)	41m 45s
build_windows (3.13)	36m 31s
build_linux (3.13)	37m 16s
build_windows (3.12)	36m 8s
build_linux (3.12)	37m 42s
array-api-conformity (3.10, false, ubuntu-22.04)	5m 0s
test_examples_linux (3.11, false, ubuntu-22.04)	7m 26s
test_linux (3.10, false, ubuntu-22.04)	11m 11s
test_linux (3.9, false, ubuntu-22.04)	11m 16s
test_linux (3.12, false, ubuntu-22.04)	11m 4s
test_linux (3.13, false, ubuntu-22.04)	10m 5s
test_linux (3.11, false, ubuntu-22.04)	10m 40s
test_windows (3.13, false, windows-2019)	14m 45s
test_windows (3.12, false, windows-2019)	14m 17s
test_windows (3.11, false, windows-2019)	14m 39s
test_windows (3.10, false, windows-2019)	14m 54s
test_windows (3.9, false, windows-2019)	13m 16s
upload_linux	0s
upload_windows	-1s
Clean up anaconda packages	-1s
	8h 38m 47s

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