[chore](Nereids) load command always could fallback (#33233)

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/LoadCommand.java

@@ -125,6 +125,7 @@ public class LoadCommand extends Command implements ForwardWithSync {
     @Override
     public void run(ConnectContext ctx, StmtExecutor executor) throws Exception {
         if (!Config.enable_nereids_load) {
+            ctx.getSessionVariable().enableFallbackToOriginalPlannerOnce();
             throw new AnalysisException("Fallback to legacy planner temporary.");
         }
         this.profile = new Profile("Query", ctx.getSessionVariable().enableProfile,