[fr] change back vlog(2) to LOG(INFO) (pytorch#142441)

Summary:
Change log message for future execution back from VLOG(2) to LOG(INFO).
This message is useful for Flight Recorder to verify that flight recorder dumps completed successfully (or not).

Test Plan: Tested manually on a mast job and noted that the INFO message was as expected.
(meta only link: https://fburl.com/mlhub/iui2tpc9)
```
[trainer5]:I1208 10:21:00.772841  7528 ProcessGroupNCCL.cpp:1294] [PG ID 0 PG GUID 0(precheck) Rank 21] future is successfully executed for: Flight recorder dump in heartbeatMonitor
```

Differential Revision: D66996439

Pull Request resolved: pytorch#142441
Approved by: https://github.com/fduwjj

Author: c-p-i-o

torch/csrc/distributed/c10d/ProcessGroupNCCL.cpp

@@ -1297,8 +1297,8 @@ bool ProcessGroupNCCL::waitForFutureOrTimeout(
     try {
       bool result = fut.get();
       if (result) {
-        VLOG(2) << logPrefix()
-                << "future is successfully executed for: " << futDescription;
+        LOG(INFO) << logPrefix()
+                  << "future is successfully executed for: " << futDescription;
         if (log) {
           data.strings["status"] = "SUCCESS";
         }