Add TODO to re-introduce metadata logging

Author: tejasd

firebase-perf/src/main/java/com/google/firebase/perf/session/gauges/GaugeManager.java

@@ -256,6 +256,7 @@ private void syncFlush(String sessionId, ApplicationProcessState appState) {
    * @return true if GaugeMetadata was logged, false otherwise.
    */
   public boolean logGaugeMetadata(String sessionId, ApplicationProcessState appState) {
+    // TODO(b/394127311): Re-introduce logging of metadata for AQS.
     if (gaugeMetadataManager != null) {
       GaugeMetric gaugeMetric =
           GaugeMetric.newBuilder()