`README.md` and `.github/workflows/build.yml` say to use different versions of Godot

[Jayman2000]

README.md says:

1. Download the latest version of the Godot 3 game engine. Godot 4 is not supported yet.

.github/workflows/build.yml says:

env:
  PROJECT_NAME: oh-my-git
  GODOT_VERSION: 3.2.3

3.2.3 is not the latest version of Godot 3 at the moment. At the moment, Godot 3.6 is the latest version of Godot 3.

It would be better if README.md and .github/workflows/build.yml both used the same version of Godot.