fix(db): drop blog slug constraint correctly

db/migrations/V027__BlogSoftDeleteAndSlugIndex.sql

@@ -2,7 +2,7 @@ ALTER TABLE blog_posts
     ADD COLUMN IF NOT EXISTS deleted_at TIMESTAMPTZ;
 
 DROP INDEX IF EXISTS idx_blog_slug;
-DROP INDEX IF EXISTS blog_posts_slug_key;
+ALTER TABLE blog_posts DROP CONSTRAINT IF EXISTS blog_posts_slug_key;
 
 CREATE UNIQUE INDEX IF NOT EXISTS ux_blog_posts_slug_active
     ON blog_posts (slug)