remove python 3.7 from matrix #852

Job	Run time
pack_pip	16s
pack_rpm (fedora, 34)	1m 18s
pack_rpm (fedora, 35)	1m 34s
pack_rpm (fedora, 36)	1m 2s
pack_deb	1m 3s
run_tests_pip_package_linux	2m 39s
run_tests_pip_package_windows	8m 14s
run_tests_deb	0s
publish_deb	0s
run_tests_rpm (fedora, 34)	4m 45s
run_tests_rpm (fedora, 35)	4m 39s
run_tests_rpm (fedora, 36)	5m 4s
publish_rpm	0s
publish_pip	0s
	30m 34s

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