Update dependencies from https://github.com/dotnet/arcade build 20210511.6 (#395)

[main] Update dependencies from dotnet/arcade

eng/Version.Details.xml

@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Dependencies>
   <ToolsetDependencies>
-    <Dependency Name="Microsoft.DotNet.Arcade.Sdk" Version="6.0.0-beta.21260.1">
+    <Dependency Name="Microsoft.DotNet.Arcade.Sdk" Version="6.0.0-beta.21261.6">
       <Uri>https://github.com/dotnet/arcade</Uri>
-      <Sha>44324e2d3563921f60b1522fccf3fef45dcfe636</Sha>
+      <Sha>c5c6ef92686f208055e884bad45d32966f0b1f95</Sha>
       <SourceBuild RepoName="arcade" ManagedOnly="true" />
     </Dependency>
   </ToolsetDependencies>

global.json

@@ -3,6 +3,6 @@
     "dotnet": "6.0.100-preview.3.21202.5"
   },
   "msbuild-sdks": {
-    "Microsoft.DotNet.Arcade.Sdk": "6.0.0-beta.21260.1"
+    "Microsoft.DotNet.Arcade.Sdk": "6.0.0-beta.21261.6"
   }
 }