Remove unused index

Index: index_environments_for_name_search_within_folder

This index was used for a query that was changed in
!146154

db/post_migrate/20240306030118_drop_index_environments_for_name_search_within_folder.rb

+# frozen_string_literal: true
+
+class DropIndexEnvironmentsForNameSearchWithinFolder < Gitlab::Database::Migration[2.2]
+  milestone '16.10'
+  disable_ddl_transaction!
+
+  INDEX_NAME = 'index_environments_for_name_search_within_folder'
+
+  def up
+    remove_concurrent_index_by_name :environments, name: INDEX_NAME
+  end
+
+  def down
+    # from structure.sql:
+    # CREATE INDEX index_environments_for_name_search_within_folder ON environments USING btree
+    # (project_id, lower(ltrim((name)::text, ((environment_type)::text || '/'::text))) varchar_pattern_ops, state);
+    add_concurrent_index :environments,
+      "project_id, lower(ltrim(name, environment_type || '/')) varchar_pattern_ops, state", name: INDEX_NAME
+  end
+end

db/schema_migrations/20240306030118

+3b81cc44ad7225df2fb73c8fc2f02d24fa3654813147475871a009414decfc0a
\ No newline at end of file

db/structure.sql

@@ -25029,8 +25029,6 @@ CREATE INDEX index_enabled_clusters_on_id ON clusters USING btree (id) WHERE (en
 CREATE INDEX index_environments_cluster_agent_id ON environments USING btree (cluster_agent_id) WHERE (cluster_agent_id IS NOT NULL);
-CREATE INDEX index_environments_for_name_search_within_folder ON environments USING btree (project_id, lower(ltrim((name)::text, ((environment_type)::text || '/'::text))) varchar_pattern_ops, state);
-
 CREATE INDEX index_environments_name_without_type ON environments USING btree (project_id, lower(ltrim(ltrim((name)::text, (environment_type)::text), '/'::text)) varchar_pattern_ops, state);
 CREATE INDEX index_environments_on_merge_request_id ON environments USING btree (merge_request_id);