ci: Set the default start_from job to be empty [skip ci]

.github/workflows/release.yml

@@ -22,9 +22,10 @@ on:
       start_from:
         description: "Specify the job to start from"
         required: false
-        default: "bump"
+        default: ""
         type: choice
         options:
+          - ""
           - bump
           - release-plz