[PLAT-13708] Last backup time initialized during HA sync

Summary: The fix https://phorge.dev.yugabyte.com/D34125 to sync remote configs removed the initialization of the local instance last backup time so subsequent updates were always null. This adds that line back in.

Test Plan: Setup HA, ensure that lastBackupTime is displayed and shows up in HA config

Reviewers: dshubin, sanketh

Reviewed By: dshubin

Subscribers: yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D34554

managed/src/main/java/com/yugabyte/yw/common/ha/PlatformReplicationManager.java

@@ -342,11 +342,12 @@ private synchronized void sync() {
                     return;
                   }
 
-                  // Update local last backup time if creating the backup succeeded.
                   config
                       .getLocal()
                       .ifPresent(
                           localInstance -> {
+                            // Update local last backup time since creating the backup succeeded.
+                            localInstance.updateLastBackup();
                             remoteInstances.forEach(
                                 instance -> {
                                   try {