fix: use DELETE FROM for consistency (#3498)
fix: use DELETE FROM for consistency (#3498)

Being consistent with [docs](https://cloud.google.com/spanner/docs/dml-syntax#delete_examples).

Co-authored-by: gcf-merge-on-green[bot] <6c7a4de7cdf40496888e303ea3f489f3cc742362@users.noreply.github.com>
Co-authored-by: Takashi Matsuo <f7c23db50f898cb58348f8ccc2931585dc97581a@google.com>
GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples