internal/postgres/symbolsearch: add missing go:generate statement
The go:generate statement was removed by mistake in a previous CL.
For golang/go#44142
Trust: Julie Qiu
Run-TryBot: Julie Qiu
TryBot-Result: kokoro
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
+//go:generate go run gen_query.go
+
package symbolsearch
import (
