MDEV-25101 Assertion !strcmp(field->name, "table_name") failed

btr_node_ptr_max_size(): Let us remove the debug assertion that was
added in MDEV-14637. The assertion assumed that no additional
indexes exist in mysql.innodb_index_stats or mysql.innodb_table_stats.
The code path is working around an incorrect definition of a table,
interpreting VARCHAR(64) as the more correct VARCHAR(199).

No test case will be added, because MDEV-24579 proves that executing
DDL on the statistics tables involves a race condition. The test
case included the following:

	ALTER TABLE mysql.innodb_index_stats ADD KEY (stat_name);
	CREATE TABLE t (a INT) ENGINE=InnoDB STATS_PERSISTENT=1;

storage/innobase/btr/btr0cur.cc

@@ -837,7 +837,6 @@ static ulint btr_node_ptr_max_size(const dict_index_t* index)
 				       TABLE_STATS_NAME)
 			       || !strcmp(index->table->name.m_name,
 					  INDEX_STATS_NAME))) {
-			ut_ad(!strcmp(field->name, "table_name"));
 			/* Interpret "table_name" as VARCHAR(199) even
 			if it was incorrectly defined as VARCHAR(64).
 			While the caller of ha_innobase enforces the