ReadMe.md(Roadmap): update threshold sigs info #3866

Job	Run time
macOS--mono-only	12m 57s
macOS--dotnet6-only	4m 53s
macOS--dotnet6-and-mono	18m 10s
windows--dotnet6-and-legacyFramework	7m 26s
windows--legacyFramework-only	11m 11s
linux-github--dotnet-and-mono	3m 46s
linux-vanilla--stockdotnet6-and-newmono	5m 39s
linux-github--dotnet-and-newmono	7m 17s
linux-vanilla--stockdotnet6-only	5m 3s
linux-vanilla--stockmono-only	5m 42s
windows--dotnet6-only	5m 50s
linux-vanilla--newmono-only	8m 31s
linux-vanilla--stockdotnet6-and-stockmono	6m 49s
conventions	1m 16s
snap_pkg_beta	7m 20s
snap_pkg	6m 14s
	1h 58m 4s

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