docs: Removed metadata comment from sample (#570)

Fixes http://b/208672646. Test looks good, going to add comment to Java and Python test files to be similar to Node.js test.

Author: nayaknishant

automl/translate_create_model.js

@@ -42,7 +42,7 @@ function main(
       model: {
         displayName: displayName,
         datasetId: datasetId,
-        translationModelMetadata: {}, // Leave unset, to use the default base model
+        translationModelMetadata: {},
       },
     };