[devops] Remove the Whitesource task. (#20088)

Ref:
https://github.com/opensource-microsoft/docs/blob/main/docs/tools/cg/announcements.md#mend-aka-whitesource-retirement-as-a-vulnerability-provider

tools/devops/automation/templates/governance-checks.yml

@@ -90,8 +90,3 @@ steps:
     PathtoPublish: $(Build.ArtifactStagingDirectory)\GuardianSuppressions
     ArtifactName: Guardian Suppressions
   condition: failed()
-
-- task: WhiteSource Bolt@20
-  displayName: "WhiteSource Bolt analysis"
-  inputs:
-    cwd: $(System.DefaultWorkingDirectory)