remove unused light_id property from shader_program

src/render_group.cpp

@@ -75,7 +75,6 @@ rgInitShaderProgram(rg_shader_program& sp, const char * vertex_code, const char
 	sp.view_matrix_id = glGetUniformLocation(sp.program_id, "view");
 	sp.projection_matrix_id = glGetUniformLocation(sp.program_id, "projection");
 	sp.normal_matrix_id = glGetUniformLocation(sp.program_id, "normal_matrix");
-	sp.lights_id = glGetUniformLocation(sp.program_id, "lights");
 	sp.num_lights_id = glGetUniformLocation(sp.program_id, "num_lights");
 
 	glDetachShader(sp.program_id, vertex_shader_id);

src/render_group.h

@@ -40,9 +40,6 @@ struct rg_shader_program
 	GLuint projection_matrix_id = 0;
 	GLuint normal_matrix_id = 0;
 	GLuint vertex_array_id = 0;
-
-	// TODO: testing lighting changes
-	GLuint lights_id = 0;
 	GLuint num_lights_id = 0;
 };