Backend.*: fix assembly version attribs #2910

Job	Run time
macOS--mono-only	5m 1s
macOS--dotnet6-only	3m 40s
windows--dotnet6-and-legacyFramework	6m 10s
linux22-github--dotnet-and-mono	3m 25s
windows--dotnet6-only	5m 59s
linux22-github--dotnet-and-newmono	3m 52s
macOS--dotnet6-and-mono	4m 58s
linux22-vanilla--stockdotnet6-and-newmono	5m 31s
linux22-vanilla--stockdotnet6-only	4m 36s
linux22-vanilla--stockmono-only	1m 22s
windows--legacyFramework-only	6m 15s
linux20-github--dotnet-and-newmono	3m 21s
linux20-vanilla--newmono-only	5m 36s
linux20-github--dotnet-and-mono	3m 27s
linux20-vanilla--stockmono-only	4m 44s
linux22-vanilla--newmono-only	6m 1s
linux22-vanilla--stockdotnet6-and-stockmono	5m 18s
conventions	0s
snap_pkg	0s
	1h 19m 16s

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