Bump actions/upload-artifact from 3 to 4 #66

Job	Run time
Build ijson and run unit tests (ubuntu-20.04, 3.7)	20s
Build ijson and run unit tests (ubuntu-20.04, 3.8)	14s
Build ijson and run unit tests (ubuntu-20.04, 3.9)	16s
Build ijson and run unit tests (ubuntu-20.04, 3.10)	16s
Build ijson and run unit tests (ubuntu-20.04, 3.11)	18s
Build ijson and run unit tests (ubuntu-20.04, 3.12)	19s
Build ijson and run unit tests (windows-2019, 3.7)	1m 7s
Build ijson and run unit tests (windows-2019, 3.8)	1m 3s
Build ijson and run unit tests (windows-2019, 3.9)	57s
Build ijson and run unit tests (windows-2019, 3.10)	1m 7s
Build ijson and run unit tests (windows-2019, 3.11)	1m 8s
Build ijson and run unit tests (windows-2019, 3.12)	1m 6s
Build ijson and run unit tests (macos-12, 3.7)	27s
Build ijson and run unit tests (macos-12, 3.8)	27s
Build ijson and run unit tests (macos-12, 3.9)	44s
Build ijson and run unit tests (macos-12, 3.10)	25s
Build ijson and run unit tests (macos-12, 3.11)	25s
Build ijson and run unit tests (macos-12, 3.12)	28s
Build ijson and run unit tests (ubuntu-20.04, pypy3.9)	36s
Build ijson and run unit tests (ubuntu-20.04, pypy3.10)	34s
	12m 17s

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