test: Fix JSON messages support unittests #1999

Job	Run time
setup-release	5s
linux-snap-packaging	10m 48s
linux-rpm-packaging	1m 35s
linux-debian-packaging	5m 17s
macosx-packaging (macos-latest, x86_64)	3m 50s
macosx-packaging (macos-latest, arm64)	3m 12s
sources	59s
windows-packaging (x64)	9m 19s
windows-packaging (x86)	8m 22s
linux-appimage	1m 51s
linux-installer	35s
publish-release	0s
publish-nightly	0s
	45m 53s

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