chore: add api_shortname to repo-metadata.json (#226)

Update .repo-metadata.json as required by go/library-data-integrity Fixes #231

Author: parthea

.repo-metadata.json

@@ -4,13 +4,14 @@
  "product_documentation": "https://cloud.google.com/iot",
  "client_documentation": "https://cloud.google.com/python/docs/reference/cloudiot/latest",
  "issue_tracker": "https://issuetracker.google.com/issues?q=status:open%20componentid:310170",
- "release_level": "ga",
+ "release_level": "stable",
  "language": "python",
  "library_type": "GAPIC_AUTO",
  "repo": "googleapis/python-iot",
  "distribution_name": "google-cloud-iot",
  "api_id": "cloudiot.googleapis.com",
  "requires_billing": true,
  "default_version": "v1",
- "codeowner_team": "@googleapis/api-iot"
+ "codeowner_team": "@googleapis/api-iot",
+ "api_shortname": "cloudiot"
 }