fix: Fixed workflow_call not being set properly for upstream checks, b=no-bug, c=workflows

Author: mr-cheffy

.github/workflows/sync-upstream.yml

@@ -8,6 +8,13 @@ on:
         required: false
         type: boolean
         default: false
+  workflow_call:
+    inputs:
+      release_candidate:
+        description: 'Set to true to sync release candidates'
+        required: false
+        type: boolean
+        default: false
 
 permissions:
   contents: write