Remove unnecessary/unreachable |return| from generated union code.

mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl

Index: mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl
index ad30fb72f4ddfa5633df7ccefb07ffa570c53898..9f6f02f0d8a525d480effd45bccce100619bfbfc 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl
@@ -31,16 +31,13 @@ bool {{class_name}}::Validate(const void* data,
 {%  for field in union.fields %}
     case {{enum_name}}::{{field.name|upper}}:
 {{ validation_macros.validate_union_field(field, union)|indent(6) }}
-    break;
 {%- endfor %}
     default:
       ReportValidationError(
           mojo::internal::VALIDATION_ERROR_UNKOWN_UNION_TAG,
           "unknown tag in {{union.name}}");
       return false;
-  };
-
-  return true;
+  }
 }
 
 {{class_name}}::{{class_name}}() {