Fix regression in our ml usage collection

A regression was introduced in elastic#74965 that caused an error to be
thrown while collecting telemetry on ML jobs. Because such exceptions
are caught and we degrade to zeroing out those counts, this one was not
caught until manual testing of telemetry.

x-pack/plugins/security_solution/server/usage/detections/detections_helpers.ts

@@ -172,7 +172,7 @@ export const getMlJobsUsage = async (ml: MlPluginSetup | undefined): Promise<MlJ
 
   if (ml) {
     try {
-      const fakeRequest = {} as KibanaRequest;
+      const fakeRequest = { headers: {} } as KibanaRequest;
       const fakeSOClient = {} as SavedObjectsClient;
 
       const modules = await ml.modulesProvider(fakeRequest, fakeSOClient).listModules();