fix deprecated usage

Author: trask

instrumentation/grpc-1.6/library/src/test/java/io/opentelemetry/instrumentation/grpc/v1_6/GrpcTest.java

@@ -53,11 +53,11 @@ protected ServerBuilder<?> configureServer(ServerBuilder<?> server) {
 
   @Override
   protected ManagedChannelBuilder<?> configureClient(ManagedChannelBuilder<?> client) {
-    return client.intercept(
-        GrpcTelemetry.builder(testing.getOpenTelemetry())
-            .setCapturedClientRequestMetadata(singletonList(CLIENT_REQUEST_METADATA_KEY))
-            .build()
-            .createClientInterceptor());
+    GrpcTelemetry.builder(testing.getOpenTelemetry())
+        .setCapturedClientRequestMetadata(singletonList(CLIENT_REQUEST_METADATA_KEY))
+        .build()
+        .addClientInterceptor(client);
+    return client;
   }
 
   @Override