drm/i915/display: remove FIXME comment for intended feature

Direction on gen >= 9 was to stop using straps and rely on VBT
indicating if the port is present or not. Remove FIXME comment since
this will never be "fixed".

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210430223808.1078010-3-lucas.demarchi@intel.com