Fix error message matching

Signed-off-by: Juan Escalada <juanescalada175@gmail.com>

plugins/scaffolder-backend/src/scaffolder/tasks/NunjucksWorkflowRunner.test.ts

@@ -208,7 +208,7 @@ describe('NunjucksWorkflowRunner', () => {
     });
 
     await expect(runner.execute(task)).rejects.toThrow(
-      "Template action with ID 'does-not-exist' is not registered.",
+      /Template action with ID 'does-not-exist' is not registered/,
     );
   });