MDEV-31473 Wrong information about innodb_checksum_algorithm in information_schema.SYSTEM_VARIABLES

MYSQL_SYSVAR_ENUM(checksum_algorithm): Correct the documentation string.
Fixes up commit 7a4fbb55 (MDEV-25105).

mysql-test/suite/sys_vars/r/sysvars_innodb.result

@@ -276,7 +276,7 @@ SESSION_VALUE	NULL
 DEFAULT_VALUE	full_crc32
 VARIABLE_SCOPE	GLOBAL
 VARIABLE_TYPE	ENUM
-VARIABLE_COMMENT	The algorithm InnoDB uses for page checksumming. Possible values are FULL_CRC32 for new files, always use CRC-32C; for old, see CRC32 below; STRICT_FULL_CRC32 for new files, always use CRC-32C; for old, see STRICT_CRC32 below; CRC32 write crc32, allow any of the other checksums to match when reading; STRICT_CRC32 write crc32, do not allow other algorithms to match when reading; INNODB write a software calculated checksum, allow any other checksums to match when reading; STRICT_INNODB write a software calculated checksum, do not allow other algorithms to match when reading; NONE write a constant magic number, do not do any checksum verification when reading; STRICT_NONE write a constant magic number, do not allow values other than that magic number when reading; Files updated when this option is set to crc32 or strict_crc32 will not be readable by MariaDB versions older than 10.0.4; new files created with full_crc32 are readable by MariaDB 10.4.3+
+VARIABLE_COMMENT	The algorithm InnoDB uses for page checksumming. Possible values are FULL_CRC32 for new files, always use CRC-32C; for old, see CRC32 below; STRICT_FULL_CRC32 for new files, always use CRC-32C; for old, see STRICT_CRC32 below; CRC32 write crc32, allow previously used algorithms to match when reading; STRICT_CRC32 write crc32, do not allow other algorithms to match when reading; New files created with full_crc32 are readable by MariaDB 10.4.3+
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL

storage/innobase/handler/ha_innodb.cc

@@ -18822,24 +18822,10 @@ static MYSQL_SYSVAR_ENUM(checksum_algorithm, srv_checksum_algorithm,
   " STRICT_FULL_CRC32"
     " for new files, always use CRC-32C; for old, see STRICT_CRC32 below;"
   " CRC32"
-    " write crc32, allow any of the other checksums to match when reading;"
+    " write crc32, allow previously used algorithms to match when reading;"
   " STRICT_CRC32"
     " write crc32, do not allow other algorithms to match when reading;"
-  " INNODB"
-    " write a software calculated checksum, allow any other checksums"
-    " to match when reading;"
-  " STRICT_INNODB"
-    " write a software calculated checksum, do not allow other algorithms"
-    " to match when reading;"
-  " NONE"
-    " write a constant magic number, do not do any checksum verification"
-    " when reading;"
-  " STRICT_NONE"
-    " write a constant magic number, do not allow values other than that"
-    " magic number when reading;"
-  " Files updated when this option is set to crc32 or strict_crc32 will"
-  " not be readable by MariaDB versions older than 10.0.4;"
-  " new files created with full_crc32 are readable by MariaDB 10.4.3+",
+  " New files created with full_crc32 are readable by MariaDB 10.4.3+",
   NULL, NULL, SRV_CHECKSUM_ALGORITHM_FULL_CRC32,
   &innodb_checksum_algorithm_typelib);