chore: update release_level in repo-metadata.json (#451)

* chore: update .repo-metadata.json

* Update .repo-metadata.json

* remove api_shortname

Co-authored-by: Tim Swast <swast@google.com>

Author: parthea

.repo-metadata.json

@@ -2,9 +2,9 @@
     "name": "pandas-gbq",
     "name_pretty": "Google BigQuery connector for pandas",
     "product_documentation": "https://cloud.google.com/bigquery",
-    "client_documentation": "https://pandas-gbq.readthedocs.io/en/latest/",
+    "client_documentation": "https://googleapis.dev/python/pandas-gbq/latest/",
     "issue_tracker": "https://github.com/googleapis/python-bigquery-pandas/issues",
-    "release_level": "beta",
+    "release_level": "preview",
     "language": "python",
     "library_type": "INTEGRATION",
     "repo": "googleapis/python-bigquery-pandas",