feat: promote to 1.0.0 (#314)

Release-As: 1.0.0

Author: chingor13

.repo-metadata.json

@@ -4,7 +4,7 @@
   "product_documentation": "https://cloud.google.com/memorystore/",
   "api_description": "is a fully-managed in-memory data store service for Memcache.",
   "client_documentation": "https://googleapis.dev/java/google-cloud-memcache/latest/index.html",
-  "release_level": "beta",
+  "release_level": "ga",
   "transport": "grpc",
   "language": "java",
   "repo": "googleapis/java-memcache",