noActionOnDelete() added to migrations.md (#9908)

* add noActionOnDelete() to migrations.md

* Update migrations.md

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Co-authored-by: Taylor Otwell <taylor@laravel.com>

migrations.md

@@ -1194,6 +1194,7 @@ An alternative, expressive syntax is also provided for these actions:
 | `$table->cascadeOnDelete();`  | Deletes should cascade.                           |
 | `$table->restrictOnDelete();` | Deletes should be restricted.                     |
 | `$table->nullOnDelete();`     | Deletes should set the foreign key value to null. |
+| `$table->noActionOnDelete();` | Prevents deletes if child records exist.          |
 
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