chore: documentation for seqno (#1977)

* chore: documentation for seqno

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: surbhigarg92

handwritten/spanner/src/transaction.ts

@@ -979,7 +979,7 @@ export class Snapshot extends EventEmitter {
    *     execution statistics for the SQL statement that
    *     produced this result set.
    * @property {string} partitionToken The partition token.
-   * @property {number} seqno The Sequence number.
+   * @property {number} seqno The Sequence number. This option is used internally and will be overridden.
    * @property {string} sql The SQL string.
    * @property {google.spanner.v1.ExecuteSqlRequest.IQueryOptions} [queryOptions]
    *     Default query options to use with the database. These options will be