fix: update it case

Signed-off-by: zacsun <zacsun@lilith.com>

Author: predator4ann

catalogs/catalog-jdbc-mysql/src/test/java/org/apache/gravitino/catalog/mysql/integration/test/CatalogMysqlIT.java

@@ -620,8 +620,7 @@ void testColumnDefaultValueConverter() {
               Literals.timestampLiteral("1983-09-05T00:00:00"), column.defaultValue());
           break;
         case "timestamp_col_3":
-          Assertions.assertEquals(
-              UnparsedExpression.of("CURRENT_TIMESTAMP(6)"), column.defaultValue());
+          Assertions.assertEquals(DEFAULT_VALUE_OF_CURRENT_TIMESTAMP, column.defaultValue());
           break;
         case "decimal_6_2_col_1":
           Assertions.assertEquals(
@@ -863,7 +862,7 @@ void testUpdateColumnDefaultValue() {
             TableChange.updateColumnDefaultValue(
                 new String[] {columns[0].name()}, Literals.of("1.2345", Types.FloatType.get())),
             TableChange.updateColumnDefaultValue(
-                new String[] {columns[1].name()}, FunctionExpression.of("current_timestamp")),
+                new String[] {columns[1].name()}, DEFAULT_VALUE_OF_CURRENT_TIMESTAMP),
             TableChange.updateColumnDefaultValue(
                 new String[] {columns[2].name()}, Literals.of("hello", Types.VarCharType.of(255))),
             TableChange.updateColumnDefaultValue(