Update Land Racer source file so it uses pose markers to generate textkeys
This change is required due to the upcoming update of the COLLADA exporter https://github.com/OpenMW/collada-exporter/pull/11 Now pose markers, which are per action, are used to generate textkeys rather than global timeline markers. Makes things easier to manage with a large number of animations and their needed textkeys.
Exporter MR and documentation needs to be updated along with this MR.