Lower the log level of the fts probe while unpacking response.

The level of TERSE or greater was set during development, we can lower
this to DEBUG now that this feature has stablized.

src/backend/fts/ftsprobe.c

@@ -621,7 +621,7 @@ probeRecordResponse(fts_segment_info *ftsInfo, PGresult *result)
 	Assert (retryRequested);
 	ftsInfo->result.retryRequested = *retryRequested;
 
-	elogif(gp_log_fts >= GPVARS_VERBOSITY_TERSE, LOG,
+	elogif(gp_log_fts >= GPVARS_VERBOSITY_DEBUG, LOG,
 		   "FTS: segment (content=%d, dbid=%d, role=%c) reported "
 		   "isMirrorUp %d, isInSync %d, isSyncRepEnabled %d, "
 		   "isRoleMirror %d, and retryRequested %d to the prober.",