Bump actions/upload-artifact from 3 to 4 #67

Job	Run time
Build ijson and run unit tests (ubuntu-20.04, 3.7)	18s
Build ijson and run unit tests (ubuntu-20.04, 3.8)	21s
Build ijson and run unit tests (ubuntu-20.04, 3.9)	19s
Build ijson and run unit tests (ubuntu-20.04, 3.10)	15s
Build ijson and run unit tests (ubuntu-20.04, 3.11)	18s
Build ijson and run unit tests (ubuntu-20.04, 3.12)	16s
Build ijson and run unit tests (windows-2019, 3.7)	1m 18s
Build ijson and run unit tests (windows-2019, 3.8)	1m 2s
Build ijson and run unit tests (windows-2019, 3.9)	1m 21s
Build ijson and run unit tests (windows-2019, 3.10)	56s
Build ijson and run unit tests (windows-2019, 3.11)	1m 21s
Build ijson and run unit tests (windows-2019, 3.12)	55s
Build ijson and run unit tests (macos-12, 3.7)	27s
Build ijson and run unit tests (macos-12, 3.8)	30s
Build ijson and run unit tests (macos-12, 3.9)	24s
Build ijson and run unit tests (macos-12, 3.10)	25s
Build ijson and run unit tests (macos-12, 3.11)	24s
Build ijson and run unit tests (macos-12, 3.12)	37s
Build ijson and run unit tests (ubuntu-20.04, pypy3.9)	31s
Build ijson and run unit tests (ubuntu-20.04, pypy3.10)	34s
	12m 32s

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