🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Bigtable/src/Admin/V2/Client/BigtableInstanceAdminClient.php

@@ -1023,7 +1023,10 @@ private function setDefaultEmulatorConfig(array $options): array
         }
 
         $options['apiEndpoint'] ??= $emulatorHost;
-        $options['transportConfig']['grpc']['stubOpts']['credentials'] ??= ChannelCredentials::createInsecure();
+        if (class_exists(ChannelCredentials::class)) {
+            $options['transportConfig']['grpc']['stubOpts']['credentials'] ??= ChannelCredentials::createInsecure();
+        }
+
         $options['credentials'] ??= new InsecureCredentialsWrapper();
         return $options;
     }

Bigtable/src/Admin/V2/Client/BigtableTableAdminClient.php

@@ -1342,7 +1342,10 @@ private function setDefaultEmulatorConfig(array $options): array
         }
 
         $options['apiEndpoint'] ??= $emulatorHost;
-        $options['transportConfig']['grpc']['stubOpts']['credentials'] ??= ChannelCredentials::createInsecure();
+        if (class_exists(ChannelCredentials::class)) {
+            $options['transportConfig']['grpc']['stubOpts']['credentials'] ??= ChannelCredentials::createInsecure();
+        }
+
         $options['credentials'] ??= new InsecureCredentialsWrapper();
         return $options;
     }

Bigtable/src/V2/Client/BigtableClient.php

@@ -562,7 +562,10 @@ private function setDefaultEmulatorConfig(array $options): array
         }
 
         $options['apiEndpoint'] ??= $emulatorHost;
-        $options['transportConfig']['grpc']['stubOpts']['credentials'] ??= ChannelCredentials::createInsecure();
+        if (class_exists(ChannelCredentials::class)) {
+            $options['transportConfig']['grpc']['stubOpts']['credentials'] ??= ChannelCredentials::createInsecure();
+        }
+
         $options['credentials'] ??= new InsecureCredentialsWrapper();
         return $options;
     }