build: update .repo-metadata.json (#64)

* build: update .repo-metadata.json

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

.repo-metadata.json

@@ -4,11 +4,12 @@
 	"product_documentation": "https://cloud.google.com/bigquery/docs/migration-intro",
 	"client_documentation": "https://cloud.google.com/nodejs/docs/reference/bigquery-migration/latest",
 	"issue_tracker": "https://github.com/googleapis/nodejs-bigquery-migration/issues",
-	"release_level": "beta",
+	"release_level": "stable",
 	"language": "nodejs",
 	"repo": "googleapis/nodejs-bigquery-migration",
 	"distribution_name": "@google-cloud/bigquery-migration",
 	"api_id": "bigquerymigration.googleapis.com",
 	"default_version": "v2",
-	"requires_billing": true
-  }
+	"requires_billing": true,
+	"library_type": "GAPIC_AUTO"
+  }

README.md

@@ -4,7 +4,7 @@
 
 # [BigQuery Migration API: Node.js Client](https://github.com/googleapis/nodejs-bigquery-migration)
 
-[![release level](https://img.shields.io/badge/release%20level-beta-yellow.svg?style=flat)](https://cloud.google.com/terms/launch-stages)
+[![release level](https://img.shields.io/badge/release%20level-stable-brightgreen.svg?style=flat)](https://cloud.google.com/terms/launch-stages)
 [![npm version](https://img.shields.io/npm/v/@google-cloud/bigquery-migration.svg)](https://www.npmjs.org/package/@google-cloud/bigquery-migration)
 
 
@@ -87,11 +87,11 @@ This library follows [Semantic Versioning](http://semver.org/).
 
 
 
+This library is considered to be **stable**. The code surface will not change in backwards-incompatible ways
+unless absolutely necessary (e.g. because of critical security issues) or with
+an extensive deprecation period. Issues and requests against **stable** libraries
+are addressed with the highest priority.
 
-This library is considered to be in **beta**. This means it is expected to be
-mostly stable while we work toward a general availability release; however,
-complete stability is not guaranteed. We will address issues and requests
-against beta libraries with a high priority.