Revert password length limit (#16087)

Author: jt2594838

integration-test/src/test/java/org/apache/iotdb/db/it/auth/IoTDBAuthIT.java

@@ -1594,4 +1594,16 @@ public void testPasswordHistoryAlter(Statement statement) throws SQLException {
           resultSet.getString("root.__system.password_history._userA.oldPassword"));
     }
   }
+
+  @Test
+  public void testChangeBackPassword() {
+    try (Connection connection = EnvFactory.getEnv().getConnection();
+        Statement statement = connection.createStatement()) {
+      statement.execute("ALTER USER root SET PASSWORD 'newPassword'");
+      statement.execute("ALTER USER root SET PASSWORD 'root'");
+    } catch (SQLException e) {
+      e.printStackTrace();
+      fail(e.getMessage());
+    }
+  }
 }

iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/utils/AuthUtils.java

@@ -53,7 +53,7 @@ public class AuthUtils {
   private static final String ROOT_PREFIX = IoTDBConstant.PATH_ROOT;
   private static final int NAME_MIN_LENGTH = 4;
   private static final int NAME_MAX_LENGTH = 32;
-  private static final int PASSWORD_MIN_LENGTH = 12;
+  private static final int PASSWORD_MIN_LENGTH = 4;
   private static final int PASSWORD_MAX_LENGTH = 32;
 
   // match number, character, and !@#$%^*()_+-=