Documentation: change references to 'Shapes Config.cginc' to use Settings Window

With the addition of the new Settings window Shapes Config.cginc is now auto-generated and features this comment:

// Do not edit this manually, this file is automatically generated
// Please use the Shapes settings window instead

Therefore the Documentation should be updated accordingly. 

Currently there are still instances in the docs that say to modify the cginc file - one in https://acegikmo.com/shapes/docs/#thickness-units and one in https://acegikmo.com/shapes/docs/#anti-aliasing