Frontend.XF.*: fix references in .fsproj files #2786

Job	Run time
macOS--dotnet6-only	4m 17s
macOS--mono-only	10m 54s
macOS--dotnet6-and-mono	21m 29s
windows--dotnet6-and-legacyFramework	8m 36s
linux-github--dotnet-and-mono	3m 53s
linux-github--dotnet-and-newmono	9m 11s
linux-vanilla--newmono-only	10m 19s
linux-vanilla--stockdotnet6-and-newmono	7m 36s
linux-vanilla--stockdotnet6-and-stockmono	9m 8s
linux-vanilla--stockdotnet6-only	6m 8s
linux-vanilla--stockmono-only	7m 28s
windows--dotnet6-only	8m 11s
windows--legacyFramework-only	19m 29s
conventions	1m 7s
snap_pkg	0s
	2h 7m 46s

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