casual_read can still be used in table definition after MDEV-31789

After MDEV-31789, first implementation;

• The --spider_casual_read option to mariadbd can no longer be used
• The GLOBAL/SESSION variable spider_casual_read can no longer be used
• However, creating a spider table with a casual_read is still possible:

  INSTALL PLUGIN Spider SONAME 'ha_spider.so';

  CREATE SERVER srv FOREIGN DATA WRAPPER MYSQL OPTIONS (SOCKET '../socket.sock',DATABASE'test',USER'',PASSWORD'');

  CREATE TABLE t1 (c INT KEY) ENGINE=Spider COMMENT='WRAPPER "mysql",srv "srv",TABLE "t", casual_read "1"';

  SHOW WARNINGS;

  SHOW CREATE TABLE t1;

  Leads to:

  11.5.0 bb-11.5-mdev-31789 0e2beea1eef4ec03eac4ea781852e133397954c3 (Optimized)
  11.5.0-opt>SHOW WARNINGS;
  +---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Level | Code | Message |
  +---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Warning | 138 | Spider table params in COMMENT or CONNECTION strings have been deprecated and will be removed in a future release. Please use table options instead. |
  | Warning | 1287 | 'casual_read' is deprecated and will be removed in a future release |
  +---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------+
  2 rows in set (0.000 sec)
  11.5.0-opt>SHOW CREATE TABLE t1;
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Table | Create Table |
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  | t1 | CREATE TABLE `t1` (
  `c` int(11) NOT NULL,
  PRIMARY KEY (`c`)
  ) ENGINE=SPIDER DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci COMMENT='WRAPPER "mysql",srv "srv",TABLE "t", casual_read "1"' |
  +-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

  It should be disabled in table creation also.