Generated vertex shaders do not need to normalize normals

[pjcozzi]

Since a normal will not remain normal during rasterization interpolation, we should not normalize normals in the generated vertex shaders like we currently do, e.g.,

v_normal = normalize(u_normalMatrix * mat3(skinMat)* a_normal);

Instead, we should just normalize in the fragment shader like we already do:

vec3 normal = normalize(v_normal);

[fabrobinet]

That was already fixed in recent changes, but not for skinned normal. done now. 28a06ca