bump pyo3 to 0.21.0 #98

Job	Run time
lint	1m 11s
test 3.9 pandas 2.0.*	2m 41s
build on linux (x86_64 - auto)	3m 21s
test 3.9 pandas 2.1.*	3m 13s
build on linux (aarch64 - auto)	3m 14s
test 3.9 pandas 2.2.*	2m 4s
build on macos (x86_64 - auto)	5m 54s
test 3.10 pandas 2.0.*	2m 57s
build on macos (aarch64 - auto)	4m 2s
test 3.10 pandas 2.1.*	2m 31s
build on windows (x86_64 - auto)	7m 2s
test 3.10 pandas 2.2.*	3m 4s
build on windows (i686 - auto)	6m 24s
test 3.11 pandas 2.0.*	57s
build on windows (aarch64 - auto)	5m 29s
test 3.11 pandas 2.1.*	1m 5s
build on linux (i686 - auto)	4m 19s
test 3.11 pandas 2.2.*	1m 29s
build on linux (armv7 - auto)	2m 53s
test 3.12 pandas 2.0.*	46s
build on linux (x86_64 - musllinux_1_1)	2m 37s
test 3.12 pandas 2.1.*	54s
test 3.12 pandas 2.2.*	48s
build on linux (aarch64 - musllinux_1_1)	2m 40s
test 3.8 pandas 2.0.*	38s
build on linux (ppc64le - auto)	2m 37s
test pypy3.8 pandas none	40s
build on linux (s390x - auto)	2m 34s
test pypy3.9 pandas none	41s
test pypy3.10 pandas none	51s
check	4s
release	0s
	1h 19m 40s

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