Typo in group create API - subgroup_creation_level should be "string" instead of "int"

https://docs.gitlab.com/ce/api/groups.html#new-group

In the table:

Attribute	Type	Required	Description
subgroup_creation_level	integer	no	Allowed to create subgroups. Can be owner (Owners), or maintainer (Maintainers).

Clearly with values like 'owner' and 'maintainer', this isn't an Int. Likewise, the GET api (https://docs.gitlab.com/ce/api/groups.html#list-groups) lists:

"subgroup_creation_level": "owner",