datastore: re-record replay test

It was broken due to a change in integration_test.go

Change-Id: I39e22a32d05ef64f536abcc76c5a0eb4a1a013db
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/43830
Reviewed-by: kokoro <[email protected]>
Reviewed-by: Jean de Klerk <[email protected]>

Author: jba