Ignore math on spaced_link_filter

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/182626



Merged-by: Brett Walker <bwalker@gitlab.com>
Approved-by: Brett Walker <bwalker@gitlab.com>
Reviewed-by: Brett Walker <bwalker@gitlab.com>
Co-authored-by: Samuel Suikkanen <samuel.suikkanen@hotmail.com>