x11/cinnamon: partially revert "Disable DOCS option"

Instead of commenting out the option, exclude it instead, as it is
to be exposed again upon future updates given that libxml2 doesn't
error out. Also remove OPTIONS_DEFAULT as DOCS and NLS are globally
enabled by default.

This partially reverts commit 3bbf0bae390af1df9a353b235b390d1f979065ef.