tidb-cloud: add CREATE VIEW to DM target user GRANT example

The privilege table on line 464 of migrate-from-mysql-using-data-migration.md
already lists CREATE VIEW as required, but the copy-pasteable GRANT example on
line 469 omits it. This causes TiDB Lightning to abort at errormanager.Init
with Error 1142 for any user who follows the example literally.

The fix brings the GRANT example in line with the privilege table.

Author: alastori

tidb-cloud/migrate-from-mysql-using-data-migration.md

@@ -466,7 +466,7 @@ For production workloads, it is recommended to have a dedicated user for replica
 For example, you can execute the following `GRANT` statement in your target TiDB Cloud cluster to grant corresponding privileges:
 
 ```sql
-GRANT CREATE, SELECT, INSERT, UPDATE, DELETE, ALTER, DROP, INDEX ON *.* TO 'dm_target_user'@'%';
+GRANT CREATE, SELECT, INSERT, UPDATE, DELETE, ALTER, DROP, INDEX, CREATE VIEW ON *.* TO 'dm_target_user'@'%';
 ```
 
 ## Step 1: Go to the Data Migration page