update generator file

Author: ohmayr

gapic/generator/generator.py

@@ -296,8 +296,8 @@ def _render_template(
                         or
                         # TODO: Remove the following conditions once support for async rest transport is GA:
                         # See related issue: https://github.com/googleapis/gapic-generator-python/issues/2121.
-                        ('async_client' in template_name and 'grpc' not in opts.transport or
-                         not api_schema.all_library_settings[api_schema.naming.proto_package].python_settings.experimental_features.rest_async_io_enabled)
+                        ('async_client' in template_name and ('grpc' not in opts.transport or
+                         not api_schema.all_library_settings[api_schema.naming.proto_package].python_settings.experimental_features.rest_async_io_enabled))
                         or
                         ('rest_asyncio' in template_name or
                          not api_schema.all_library_settings[api_schema.naming.proto_package].python_settings.experimental_features.rest_async_io_enabled)