[fix](variable persist) fix regression test test_mtmv (apache#58869)

Author: feiniaofeiafei

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/agg/AggregateFunction.java

@@ -154,7 +154,7 @@ public String toString() {
                 .stream()
                 .map(Expression::toString)
                 .collect(Collectors.joining(", "));
-        return getName() + "(" + (distinct ? "DISTINCT " : "") + args + ")" + "__" + getSignature();
+        return getName() + "(" + (distinct ? "DISTINCT " : "") + args + ")";
     }
 
     @Override

regression-test/suites/nereids_p0/variables_persist/test_mtmv.groovy

@@ -117,10 +117,7 @@ suite("test_mtmv") {
     """
     sql "set enable_decimal256=true;"
     qt_test_normalizeagg "select  /*+use_mv(mv_pre_mv_rewrite)*/ col_sum from v_test_agg_distinct_reverse_rewrite  order by 1;"
-    explain {
-        sql "select /*+use_mv(mv_pre_mv_rewrite)*/  col_sum from v_test_agg_distinct_reverse_rewrite;"
-        contains "mv_pre_mv_rewrite chose"
-    }
+    mv_rewrite_success_without_check_chosen("select /*+use_mv(mv_pre_mv_rewrite)*/  col_sum from v_test_agg_distinct_reverse_rewrite;", "mv_pre_mv_rewrite")
     sql "drop materialized view  if exists mv_pre_mv_rewrite;"