test(bigtable): abbrviate instance and cluster names to avoid length overrun (#4973)

diff --git a/bigtable/integration_test.go b/bigtable/integration_test.go
index 980a0d1..dd2c0f2 100644
--- a/bigtable/integration_test.go
+++ b/bigtable/integration_test.go
@@ -2427,7 +2427,7 @@
 		t.Fatalf("NewInstanceAdminClient: %v", err)
 	}
 	defer iAdminClient.Close()
-	uniqueID := make([]byte, 8)
+	uniqueID := make([]byte, 4)
 	_, err = rand.Read(uniqueID)
 	diffInstance := fmt.Sprintf("%s-d-%x", testEnv.Config().Instance, uniqueID)
 	diffCluster := sourceCluster + "-d"
diff --git a/internal/kokoro/continuous.sh b/internal/kokoro/continuous.sh
index 99310f0..48e71a8 100755
--- a/internal/kokoro/continuous.sh
+++ b/internal/kokoro/continuous.sh
@@ -38,11 +38,11 @@
 export GCLOUD_TESTS_GOLANG_PROFILER_ZONE="us-west1-b"
 
 # Bigtable integration tests expect an existing instance and cluster
-#  ❯ cbt createinstance gcloud-bt-it-tests-instance gcloud-bt-it-tests-instance \
-#    gcloud-bt-it-tests-cluster us-west1-b 1 SSD
+#  ❯ cbt createinstance gc-bt-it-instance gc-bt-it-instance \
+#    gc-bt-it-cluster us-west1-b 1 SSD
 export GCLOUD_TESTS_BIGTABLE_KEYRING=projects/dulcet-port-762/locations/us-central1/keyRings/go-integration-test
-export GCLOUD_TESTS_BIGTABLE_CLUSTER="gcloud-bt-it-tests-cluster"
-export GCLOUD_TESTS_BIGTABLE_INSTANCE="gcloud-bt-it-tests-instance"
+export GCLOUD_TESTS_BIGTABLE_CLUSTER="gc-bt-it-cluster"
+export GCLOUD_TESTS_BIGTABLE_INSTANCE="gc-bt-it-instance"
 
 # Fail on any error
 set -eo pipefail