ci: handle missing manager APKs gracefully

Signed-off-by: Ahmed Al-Nassif <mr.ahmed.nassif@gmail.com>

.github/workflows/main.yml

@@ -535,7 +535,7 @@ jobs:
         with:
           name: manager-apks
           path: manager_apks/
-          if-no-files-found: error
+          if-no-files-found: warn
 
   publish-manager-artifacts:
     needs: list-manager-apks