chore(deps): update dependency google-cloud-datastore to v1.15.3 (#59)

Author: renovate-bot

dlp/snippets/requirements.txt

@@ -1,5 +1,5 @@
 google-cloud-dlp==2.0.0
 google-cloud-storage==1.31.2
 google-cloud-pubsub==1.7.0
-google-cloud-datastore==1.15.0
+google-cloud-datastore==1.15.3
 google-cloud-bigquery==2.1.0