chore: update release-level in .repo-metadata.json (#48)

Author: Neenu1995

.repo-metadata.json

@@ -4,7 +4,7 @@
     "product_documentation": "https://cloud.google.com/logging/docs",
     "api_description": "Java EE idiomatic servlet container initializer to capture Http request context.",
     "client_documentation": "https://cloud.google.com/java/docs/reference/google-cloud-logging-servlet-initializer/latest/history",
-    "release_level": "alpha",
+    "release_level": "preview",
     "language": "java",
     "min_java_version": 8,
     "repo": "googleapis/java-logging-servlet-initializer",