spanner: make PartitionedUpdate treat query parameters
spanner: make PartitionedUpdate treat query parameters

Fixes #1472

Change-Id: I609fdd0897c91e9a4e77a38251316113a1a9e3d3
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/41450
Reviewed-by: Jean de Klerk <605b93664484fed1e671a07bff68da39e73d0174@google.com>

googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go