Update doc

htdocs/install/mysql/migration/repair.sql

@@ -13,11 +13,12 @@
 -- flush privileges;
 
 
--- Requests to change character set and collation of a column
+-- Requests to change character set and collation of a varchar column.
+-- utf8 and utf8_unicode_ci is recommended (or even better utf8mb4 and utf8mb4_unicode_ci with mysql 5.5.3+)
 
 -- ALTER TABLE llx_accounting_account MODIFY account_number VARCHAR(20) CHARACTER SET utf8;
 -- ALTER TABLE llx_accounting_account MODIFY account_number VARCHAR(20) COLLATE utf8_unicode_ci;
--- You can check with "show full columns from llx_accountingaccount";
+-- You can check with "show full columns from llx_accounting_account";