chore: add api_shortname to repo-metadata.json (#745)

* chore: update .repo-metadata.json

* revert

* Set release_level to stable

Co-authored-by: Vikash Singh <3116482+vi3k6i5@users.noreply.github.com>

Author: parthea

.repo-metadata.json

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