Add migration to drop `smiles` table

db/migrate/20220705212912_drop_smiles_table.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class DropSmilesTable < ActiveRecord::Migration[6.1]
+  def up
+    drop_table :smiles
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end