fix: Allow --experimental on reindex_studio as a no-op (#38433)

Putting this flag back as a backcompat no-op will smooth
out the transition for developers and operators.

Follows up on: 9af9d8f
Related: overhangio/tutor#1374

Author: kdmccormick

openedx/core/djangoapps/content/search/management/commands/reindex_studio.py

@@ -43,6 +43,12 @@ class Command(BaseCommand):
 
     def add_arguments(self, parser):
         # Removed flags — provide clear error messages for operators with old automation.
+        parser.add_argument(
+            "--experimental",
+            action="store_true",
+            default=False,
+            help="(Removed) reindex_studio is no longer experimental.",
+        )
         parser.add_argument(
             "--reset",
             action="store_true",
@@ -85,6 +91,11 @@ def handle(self, *args, **options):
                 "The --incremental flag has been removed. "
                 "Incremental population is now the default behavior of this command."
             )
+        if options["experimental"]:
+            log.warning(
+                "The --experimental flag has been removed. "
+                "reindex_studio is now a stable command, so the flag is no longer necessary."
+            )
 
         result = rebuild_index_incremental.delay()