chore: complete migration of sqlalchemy-spanner to librarian (#16749)

Author: jskeet

librarian.yaml

@@ -4632,7 +4632,6 @@ libraries:
       client_documentation_override: https://googleapis.dev/python/sqlalchemy-bigquery/latest/index.html
   - name: sqlalchemy-spanner
     version: 1.17.3
-    skip_generate: true
     python:
       library_type: INTEGRATION
       name_pretty_override: Spanner dialect for SQLAlchemy

packages/sqlalchemy-spanner/.repo-metadata.json

@@ -1,14 +1,13 @@
 {
-    "name": "sqlalchemy-spanner",
-    "name_pretty": "Spanner dialect for SQLAlchemy",
-    "product_documentation": "https://cloud.google.com/spanner/docs",
+    "api_shortname": "sqlalchemy-spanner",
     "client_documentation": "https://github.com/googleapis/python-spanner-sqlalchemy",
+    "distribution_name": "sqlalchemy-spanner",
     "issue_tracker": "https://issuetracker.google.com/issues?q=componentid:190851%2B%20status:open",
-    "release_level": "stable",
     "language": "python",
     "library_type": "INTEGRATION",
-    "repo": "googleapis/google-cloud-python",
-    "distribution_name": "sqlalchemy-spanner",
-    "requires_billing": true,
-    "api_shortname": "sqlalchemy-spanner"
-}
+    "name": "sqlalchemy-spanner",
+    "name_pretty": "Spanner dialect for SQLAlchemy",
+    "product_documentation": "https://cloud.google.com/spanner/docs",
+    "release_level": "stable",
+    "repo": "googleapis/google-cloud-python"
+}