Revert "perf: add index on labels columns to library_item table"

This reverts commit 706277085a.

packages/db/migrations/0186.do.labels_index_on_library_item.sql

@@ -1,5 +0,0 @@
--- Type: DO
--- Name: labels_index_on_library_item
--- Description: Add index on labels columns to library_item tables for better performance
-
-CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_library_item_state_label_names ON omnivore.library_item USING GIN (lower(array_cat(label_names, highlight_labels)::text));

packages/db/migrations/0186.undo.labels_index_on_library_item.sql

@@ -1,9 +0,0 @@
--- Type: UNDO
--- Name: more_index_on_library_item
--- Description: Add index on labels columns to library_item tables for better performance
-
-BEGIN;
-
-DROP INDEX IF EXISTS idx_library_item_state_label_names;
-
-COMMIT;