Remove the generic argument from Drawable::draw

[ozkriff]

Closes #556

Un-nested mesh creation calls because of the conflicting ctx arguments:

227 |         graphics::draw(
    |         -------------- first borrow later used by call
228 |             ctx,
    |             --- first mutable borrow occurs here
229 |             &graphics::Mesh::new_rectangle(ctx, graphics::DrawMode::Fill, self.pos.into(), color)?,
    |                                            ^^^ second mutable borrow occurs here

What do you think?