chore: Close gRPC Identity client (#1628)

diff --git a/showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITCrud.java b/showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITCrud.java
index 1600d86..356ea51 100644
--- a/showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITCrud.java
+++ b/showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITCrud.java
@@ -60,6 +60,7 @@
 
   @After
   public void cleanup() {
+    grpcClient.close();
     httpJsonClient.close();
   }