test(bigtable): modify CI Encryption Key Name used by TestIntegration_AdminEncryptionInfo (#5043)

#4173 

Allow test to use later versions (not just v1)
Use a regional key as the other one is no longer regional.
diff --git a/bigtable/integration_test.go b/bigtable/integration_test.go
index f44f870..34e3548 100644
--- a/bigtable/integration_test.go
+++ b/bigtable/integration_test.go
@@ -1613,7 +1613,7 @@
 		t.Fatalf("Creating table: %v", err)
 	}
 
-	encryptionKeyVersion := kmsKeyName + "/cryptoKeyVersions/1"
+	var encryptionKeyVersion string
 
 	// The encryption info can take 30-300s (currently about 120-190s) to
 	// become ready.
@@ -1623,8 +1623,8 @@
 			t.Fatalf("EncryptionInfo: %v", err)
 		}
 
-		kmsKeyVersion := encryptionInfo[clusterID][0].KMSKeyVersion
-		if kmsKeyVersion != "" {
+		encryptionKeyVersion = encryptionInfo[clusterID][0].KMSKeyVersion
+		if encryptionKeyVersion != "" {
 			break
 		}
 
diff --git a/internal/kokoro/continuous.sh b/internal/kokoro/continuous.sh
index 48e71a8..286f2cb 100755
--- a/internal/kokoro/continuous.sh
+++ b/internal/kokoro/continuous.sh
@@ -40,7 +40,7 @@
 # Bigtable integration tests expect an existing instance and cluster
 #  ❯ 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_KEYRING=projects/dulcet-port-762/locations/us-central1/keyRings/go-integration-test-regional
 export GCLOUD_TESTS_BIGTABLE_CLUSTER="gc-bt-it-cluster"
 export GCLOUD_TESTS_BIGTABLE_INSTANCE="gc-bt-it-instance"