refactor: move java-showcase to root

Author: chingor13

generation_config.yaml

@@ -3023,8 +3023,8 @@ libraries:
   release_level: stable
   client_documentation: https://cloud.google.com/java/docs/reference/proto-google-common-protos/latest/history
   distribution_name: com.google.api.grpc:proto-google-common-protos
-  excluded_dependencies: "proto-google-common-protos,grpc-google-common-protos,proto-google-common-protos-parent"
-  excluded_poms: "proto-google-common-protos-bom,proto-google-common-protos"
+  excluded_dependencies: proto-google-common-protos,grpc-google-common-protos,proto-google-common-protos-parent
+  excluded_poms: proto-google-common-protos-bom,proto-google-common-protos
   library_type: OTHER
   GAPICs:
   - proto_path: google/api
@@ -3039,3 +3039,12 @@ libraries:
   - proto_path: google/rpc/context
   - proto_path: google/shopping/type
   - proto_path: google/type
+- api_shortname: showcase
+  excluded_poms: gapic-showcase-bom
+  name_pretty: Showcase
+  api_description: Showcase module
+  product_documentation: https://cloud.google.com/dummy
+  distribution_name: com.google.cloud:gapic-showcase
+  library_type: OTHER
+  GAPICs:
+  - proto_path: schema/google/showcase/v1beta1