ReadMe.md: replace GitCoin with LB #3956

Job	Run time
linux-vanilla--stockdotnet6-and-newmono	6m 28s
linux-vanilla--newmono-only	9m 14s
linux-github--dotnet-and-mono	4m 49s
linux-github--dotnet-and-newmono	7m 48s
linux-vanilla--stockdotnet6-and-stockmono	7m 22s
linux-vanilla--stockdotnet6-only	5m 41s
linux-vanilla--stockmono-only	6m 23s
macOS--dotnet6-and-mono	13m 12s
macOS--dotnet6-only	5m 50s
macOS--mono-only	13m 47s
windows--dotnet6-and-legacyFramework	6m 36s
windows--dotnet6-only	5m 34s
windows--legacyFramework-only	22m 45s
conventions	1m 27s
snap_pkg	7m 32s
snap_pkg_beta	7m 27s
	2h 11m 55s

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