Don't display immutable tag option for non Ultimate lincenses

Context

The container registry immutable tags feature is only available in the Ultimate tier.

Problem

Right now we're displaying the "immutable" option when creating protected tags in instances/group with no Ultimate license. While the functionality is preserved (i.e., there is an error saying that an Ultimate license is required when attempting to create an immutable rule), it seems unnecessary to display the option given that it's not technically available.