Use new migration rather than modifying existing in place

This won't change the impact, but ensures deployments definitely have a reset counter, even if they've already released 5.0.

wagtail/contrib/search_promotions/migrations/0004_copy_queries.py

@@ -1,18 +1,6 @@
 # Generated by Django 3.1.8 on 2021-06-22 14:56
 
 from django.db import migrations
-from django.core.management.color import no_style
-
-
-def reset_search_promotion_sequence(apps, schema_editor):
-    Query = apps.get_model("wagtailsearchpromotions.Query")
-    QueryDailyHits = apps.get_model("wagtailsearchpromotions.QueryDailyHits")
-
-    statements = schema_editor.connection.ops.sequence_reset_sql(
-        no_style(), [Query, QueryDailyHits]
-    )
-    for statement in statements:
-        schema_editor.execute(statement)
 
 
 class Migration(migrations.Migration):
@@ -39,9 +27,4 @@ class Migration(migrations.Migration):
             """,
             "",
         ),
-        # We set an explicit pk instead of relying on auto-incrementation,
-        # so we need to reset the database sequence.
-        migrations.RunPython(
-            reset_search_promotion_sequence, migrations.RunPython.noop
-        ),
     ]

wagtail/contrib/search_promotions/migrations/0006_reset_query_sequence.py

@@ -0,0 +1,31 @@
+# Generated by Django 4.0.10 on 2023-09-07 10:41
+
+from django.db import migrations
+from django.core.management.color import no_style
+
+
+def reset_search_promotion_sequence(apps, schema_editor):
+    """
+    We set an explicit pk instead of relying on auto-incrementation in migration 0004,
+    so we need to reset the database sequence.
+    """
+    Query = apps.get_model("wagtailsearchpromotions.Query")
+    QueryDailyHits = apps.get_model("wagtailsearchpromotions.QueryDailyHits")
+
+    statements = schema_editor.connection.ops.sequence_reset_sql(
+        no_style(), [Query, QueryDailyHits]
+    )
+    for statement in statements:
+        schema_editor.execute(statement)
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("wagtailsearchpromotions", "0005_switch_query_model"),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            reset_search_promotion_sequence, migrations.RunPython.noop
+        ),
+    ]