Don't build all wheels all the time #11

Job	Run time
Build ijson and run unit tests (ubuntu-20.04, 3.7)	25s
Build ijson and run unit tests (ubuntu-20.04, 3.8)	14s
Build ijson and run unit tests (ubuntu-20.04, 3.9)	17s
Build ijson and run unit tests (ubuntu-20.04, 3.10)	17s
Build ijson and run unit tests (ubuntu-20.04, 3.11)	15s
Build ijson and run unit tests (ubuntu-20.04, 3.12)	15s
Build ijson and run unit tests (windows-2019, 3.7)	40s
Build ijson and run unit tests (windows-2019, 3.8)	39s
Build ijson and run unit tests (windows-2019, 3.9)	57s
Build ijson and run unit tests (windows-2019, 3.10)	58s
Build ijson and run unit tests (windows-2019, 3.11)	1m 14s
Build ijson and run unit tests (windows-2019, 3.12)	1m 1s
Build ijson and run unit tests (macos-12, 3.7)	38s
Build ijson and run unit tests (macos-12, 3.8)	35s
Build ijson and run unit tests (macos-12, 3.9)	33s
Build ijson and run unit tests (macos-12, 3.10)	29s
Build ijson and run unit tests (macos-12, 3.11)	26s
Build ijson and run unit tests (macos-12, 3.12)	28s
Build ijson and run unit tests (ubuntu-20.04, pypy3.9)	51s
Build ijson and run unit tests (ubuntu-20.04, pypy3.10)	23s
	11m 35s

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