Update changelog for 1.39.11 release #765

Job	Run time
Test (ubuntu-20.04, OmniSharp.MSBuild.Tests,OmniSharp.Roslyn.CSharp.Tests,OmniSharp.Cake.Tests,Om...	23m 30s
Test (ubuntu-20.04, OmniSharp.MSBuild.Tests,OmniSharp.Roslyn.CSharp.Tests,OmniSharp.Cake.Tests,Om...	23m 30s
Test (ubuntu-20.04, OmniSharp.DotNetTest.Tests)	10m 25s
Test (ubuntu-20.04, OmniSharp.DotNetTest.Tests)	10m 25s
Test (windows-2022, OmniSharp.MSBuild.Tests,OmniSharp.Roslyn.CSharp.Tests,OmniSharp.Cake.Tests,Om...	26m 16s
Test (windows-2022, OmniSharp.MSBuild.Tests,OmniSharp.Roslyn.CSharp.Tests,OmniSharp.Cake.Tests,Om...	26m 16s
Test (windows-2022, OmniSharp.DotNetTest.Tests)	13m 9s
Test (windows-2022, OmniSharp.DotNetTest.Tests)	13m 9s
Test (macos-11, OmniSharp.MSBuild.Tests,OmniSharp.Roslyn.CSharp.Tests,OmniSharp.Cake.Tests,OmniSh...	5m 14s
Test (macos-11, OmniSharp.MSBuild.Tests,OmniSharp.Roslyn.CSharp.Tests,OmniSharp.Cake.Tests,OmniSh...	34m 32s
Test (macos-11, OmniSharp.DotNetTest.Tests)	18m 0s
Test (macos-11, OmniSharp.DotNetTest.Tests)	18m 0s
	3h 42m 26s

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