[World] Mars world sand texture not loading

[renzodamgo]

Mars world texture is gray, it should use sand_pebbles.png texture.

Acceptance Criteria:

• Mars world should render with texture inside the gazebo simulation

[renzodamgo]

It worked but then it stopped working, need to apply materials txt changes and reboot.
Maybe there is an issue that Gazebo Assets are not being updated or are cached when I run the simulation.