feat: Mark stable to prepare for 1.0.0 release (#198)

Mark stable for 1.0.0 release

.repo-metadata.json

@@ -5,7 +5,7 @@
   "product_documentation": "https://cloud.google.com/pubsub/docs/",
   "client_documentation": "https://cloud.google.com/java/docs/reference/pubsub-group-kafka-connector/latest/history",
   "api_description": "The Pub/Sub Group Kafka Connector is developed to work with Kafka Connect to publish messages from Kafka to Google Cloud Pub/Sub or Pub/Sub Lite and vice versa.",
-  "release_level": "preview",
+  "release_level": "stable",
   "language": "java",
   "min_java_version": 8,
   "repo": "googleapis/java-pubsub-group-kafka-connector",

README.md

@@ -1,7 +1,7 @@
 # Google Cloud Pub/Sub Group Kafka Connector
 
 [![Maven][maven-version-image]][maven-version-link]
-![preview][preview-stability]
+![Stability][stable-stability]
 
 The Google Cloud Pub/Sub Group Kafka Connector library provides Google Cloud
 Platform (GCP) first-party connectors for Pub/Sub products with
@@ -412,4 +412,3 @@ Apache 2.0 - See [LICENSE](LICENSE) for more information.
 [maven-version-image]: https://img.shields.io/maven-central/v/com.google.cloud/pubsub-group-kafka-connector.svg
 [maven-version-link]: https://search.maven.org/search?q=g:com.google.cloud%20AND%20a:pubsub-group-kafka-connector&core=gav
 [stable-stability]: https://img.shields.io/badge/stability-stable-green
-[preview-stability]: https://img.shields.io/badge/stability-preview-yellow