Hi Miguel, when you open the include in change mode, it'll ask for access key (which I guess you already have). It should open it in the Modification Assistant mode. From there just select the line and click Delete button in the toolbar:
I suspect you're trying to do this as an enhancement and those can't be used to delete existing code (from what I understand). This is not an enhancement, it's a "core modification". Normally we don't do those, but this is needed only temporary till we upgrade to the support pack that has updated FM.