remove camera_t's "relativex" option from Lua stuff, it's unused anyway (todo:...

remove camera_t's "relativex" option from Lua stuff, it's unused anyway (todo: possibly remove said variable from existence altogether? Some disabled code still uses it though)

git-svn-id: https://code.orospakr.ca/svn/srb2/trunk@9036 6de4a73c-47e2-0310-b8c1-93d6ecd3f8cd