fix(gcp_stackdriver_metrics sink): Call function to regenerate auth token (#17297)

Author: spencergilbert

src/sinks/gcp/stackdriver_metrics.rs

@@ -108,6 +108,7 @@ impl SinkConfig for StackdriverConfig {
         let client = HttpClient::new(tls_settings, cx.proxy())?;
         let batch_settings = self.batch.into_batch_settings()?;
 
+        auth.spawn_regenerate_token();
         let sink = HttpEventSink {
             config: self.clone(),
             started,