refactor: enable 'no-copy'

erpnext/accounts/doctype/journal_entry/journal_entry.json

@@ -541,6 +541,7 @@
    "fieldname": "is_system_generated",
    "fieldtype": "Check",
    "label": "Is System Generated",
+   "no_copy": 1,
    "read_only": 1
   }
  ],
@@ -548,7 +549,7 @@
  "idx": 176,
  "is_submittable": 1,
  "links": [],
- "modified": "2023-08-10 09:54:52.060639",
+ "modified": "2023-08-10 14:32:22.366895",
  "modified_by": "Administrator",
  "module": "Accounts",
  "name": "Journal Entry",