Fix manual ESRP publish pipeline runs (#5961)

Use the queued build source version as the non-empty default for the optional commit SHA override, allowing Azure DevOps to enable manual runs for both publish pipelines.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Co-authored-by: TheLarkInn <TheLarkInn@users.noreply.github.com>
Copilot-Session: 4b8af35a-a354-47a4-803f-f77c9e057d67

Author: TheLarkInn

common/config/azure-pipelines/esrp-publish-rush.yaml

@@ -29,7 +29,7 @@ parameters:
   - name: CommitShaOverride
     displayName: 'Commit SHA Override (for testing)'
     type: string
-    default: ''
+    default: $(Build.SourceVersion)
 
 variables:
   - name: FORCE_COLOR

common/config/azure-pipelines/esrp-publish-rushstack.yaml

@@ -29,7 +29,7 @@ parameters:
   - name: CommitShaOverride
     displayName: 'Commit SHA Override (for testing)'
     type: string
-    default: ''
+    default: $(Build.SourceVersion)
 
 variables:
   - name: FORCE_COLOR