Fix bug for show create table statement with unique key types (#2231)

fe/src/main/java/org/apache/doris/analysis/CreateTableStmt.java

@@ -340,7 +340,7 @@ public class CreateTableStmt extends DdlStmt {
                     col.setAggregationTypeImplicit(true);
                 }
             }
-            columns.add(columnDef.toColumn());
+            columns.add(col);
         }
     }