Docs: warn parallelism > 1 doesn't work for migration procedures (#…

…11417)

docs/docs/spark-procedures.md

@@ -586,6 +586,9 @@ See [`migrate`](#migrate) to replace an existing table with an Iceberg table.
 | `properties`  | ️   | map<string, string> | Properties to add to the newly created table |
 | `parallelism` |    | int | Number of threads to use for file reading (defaults to 1) |
 
+!!! warning
+    There's a [known issue with `parallelism > 1`](https://github.com/apache/iceberg/issues/11147) that is scheduled to be fixed in the next release.
+
 #### Output
 
 | Output Name | Type | Description |
@@ -629,6 +632,9 @@ By default, the original table is retained with the name `table_BACKUP_`.
 | `backup_table_name` |  | string | Name of the table that will be retained as backup (defaults to `table_BACKUP_`) |
 | `parallelism` |   | int | Number of threads to use for file reading (defaults to 1) |
 
+!!! warning
+    There's a [known issue with `parallelism > 1`](https://github.com/apache/iceberg/issues/11147) that is scheduled to be fixed in the next release.
+
 #### Output
 
 | Output Name | Type | Description |
@@ -675,6 +681,9 @@ Warning : Schema is not validated, adding files with different schema to the Ice
 
 Warning : Files added by this method can be physically deleted by Iceberg operations
 
+!!! warning
+    There's a [known issue with `parallelism > 1`](https://github.com/apache/iceberg/issues/11147) that is scheduled to be fixed in the next release.
+
 #### Output
 
 | Output Name               | Type | Description                                       |