A user with "GRANT_REVOKE_ON_ANY_OBJECT" privilege can't revoke a role from himself if he is not a grantor

[DmitriyStarodubov]

Here are the steps to reproduce:

isql -u sysdba -p masterkey employee
Database: employee, User: SYSDBA
SQL> create user adm password 'adm';
SQL> grant RDB$ADMIN to adm;
SQL> exit;

isql -u adm -p adm -r RDB$ADMIN employee
Database: employee, User: ADM, Role: RDB$ADMIN
SQL> create role test_role;
SQL> grant test_role to sysdba;
SQL> exit;

isql -u sysdba -p masterkey employee
Database: employee, User: SYSDBA
SQL> revoke test_role from sysdba;
Statement failed, SQLSTATE = 42000
unsuccessful metadata update
-REVOKE failed
-SYSDBA is not grantor of ROLE on TEST_ROLE to SYSDBA.

It's because of a complex condition in the GrantRevokeNode::grantRevoke method in which the check of the "GRANT_REVOKE_ON_ANY_OBJECT" privilege comes after checking that the user has granted the permission themselves.
This condition have been added in #5527.
But I see no reason to prevent a user with the "GRANT_REVOKE_ON_ANY_OBJECT" privilege from revoking permissions.