Bump golang.org/x/sync from 0.7.0 to 0.8.0 #1114

Job	Run time
quicktests	55s
lint	56s
coverage	1m 51s
unittests (ubuntu-22.04)	1m 28s
unittests (ubuntu-latest-arm-8-cores)	3m 55s
unittests (macos-13)	2m 48s
unittests (self-hosted, macos, arm64)	12m 53s
unittests (windows-2022)	3m 40s
Build postcli (ubuntu-22.04)	30s
Build postcli (ubuntu-latest-arm-8-cores)	4m 41s
Build postcli (macos-13)	1m 46s
Build postcli (self-hosted, macos, arm64)	12m 21s
Build postcli (windows-2022)	1m 48s
Publish release	0s
	49m 32s

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