feat: Deprecate the structures script.

This script has been copied into edx-platform in
openedx/edx-platform#34328 and so we want to
make sure we leave a warning here.

README.md

@@ -25,6 +25,7 @@ and migrated [here](https://github.com/openedx/edx-platform/tree/master/scripts/
 - `tubular/scripts/retirement_archive_and_cleanup.py`
 - `tubular/scripts/retirement_bulk_status_update.py`
 - `tubular/scripts/retirement_partner_report.py`
+- `tubular/scripts/structures.py`
 
 This decision was made to streamline and consolidate our codebase.
 

tubular/scripts/structures.py

@@ -16,6 +16,7 @@
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 from tubular.splitmongo import ChangePlan, SplitMongoBackend  # pylint: disable=wrong-import-position
+from tubular.utils.deprecation import deprecated_script
 
 LOG = logging.getLogger('structures')
 click_log.basic_config(LOG)
@@ -38,6 +39,7 @@
     help='Name of the edX Mongo database containing the course structures to prune.'
 )
 @click.pass_context
+@deprecated_script
 def cli(ctx, connection, database_name):
     """
     Recover space on MongoDB for edx-platform by deleting unreachable,