Remove unused width and height properties from flat and standard shaders

[mrxz]

Description:
The flat and standard shaders both list a width and height property. These properties go unused and can thus be removed. Originally they seemed to have been used for video textures to indicate the dimensions of the video element, however this is no longer the case. The only reference I could find was in a material unit test.

This PR simply removes the properties. A good indicator that it isn't needed might be the phong shader which never had them to begin with, but supports video textures in the same way as flat and standard do.

Changes proposed:

• Remove width and height properties from flat and standard shaders

[dmarcos]

Thanks