Update 16.8 insertion target (dotnet#9952)

Author: brettfo

azure-pipelines.yml

@@ -447,6 +447,6 @@ stages:
   - template: eng/release/insert-into-vs.yml
     parameters:
       componentBranchName: refs/heads/release/dev16.8
-      insertTargetBranch: master
+      insertTargetBranch: main
       insertTeamEmail: [email protected]
       insertTeamName: 'F#'