ci(hana): release-please manages db-service dep (#1377)

With this, `release-please` will enforce that dependencies within the
workspace are automatically bumped. Effectively, this will update all
our dbs if the `db-service` version is increased.

---

from the [release-please
docs](https://github.com/googleapis/release-please/blob/main/docs/manifest-releaser.md#node-workspace):

The node-workspace plugin builds a graph of local node packages
configured in release-please-config.json and the dependency
relationships between them. It looks at what packages were updated by
release-please and updates their reference in other packages'
dependencies lists. Even when a particular package was not updated by
release-please, if a dependency did have an update, it will be patch
bump the package, create a changelog entry, and add it to the list of PR
changes. Under the hood, this plugin adapts specific dependency graph
building and updating functionality from the popular
[lerna](https://github.com/lerna/lerna) tool.

Author: patricebender

release-please-config.json

@@ -1,13 +1,12 @@
 {
+  "plugins": [
+    "node-workspace"
+  ],
   "packages": {
-    "db-service": {
-    },
-    "sqlite": {
-    },
-    "postgres": {
-    },
-    "hana": {
-    }
+    "db-service": {},
+    "sqlite": {},
+    "postgres": {},
+    "hana": {}
   },
   "changelog-sections": [
     {