Revert "Skip checkout for Set_variables job (#4706)" (#4807)

This reverts commit 57947b0.

Author: localconst

.vsts.release.yml

@@ -75,10 +75,6 @@ extends:
       - job: Set_variables
         displayName: Set release-specific variables
         steps:
-        # There's no need to clone the repo since no sources are used.
-        - checkout: none
-          displayName: Skip repo clone
-
         - pwsh: |
             $isBuildStageOnly = [System.Convert]::ToBoolean('${{ parameters.buildStageOnly }}')
             $buildReason = '$(Build.Reason)'