Revert OpenGL compatibility version

[p-yukusai]

We have decided to give up on support for OpenGL 3.1 and opt to keep using OpenGL 3.3, these are the reasons why:

1. The main target of our compatibility efforts, Intel integrated graphics cards, don't render the application properly anyway due to faulty drivers, even with compatible 3.1 code.
2. OpenGL 3.1 is very limiting and annoying to maintain.
3. Newer systems either lack proper support for OpenGL 3.1 (such as M1 chips for MacOS), or they have a lot of issues with it (Newer Intel integrated graphics chips).