CI: Use correct godot-cpp branch

[dsnopek]

Currently, it seems like CI using the master branch of godot-cpp, rather than the one we have configured.

Let's see if this works!

[dsnopek]

This seems to work:

Previously, it wouldn't list ref at all

This too:

[Repiteo]

Ohh, good catch!

[Repiteo]

It is odd though, that the env section in godot-cpp-build/action.yml seemed to not do anything. Maybe called actions don't store environment variables the same as actual workflows? In any case, you can remove lines 4-6 on that file, as they don't seem to work.

[dsnopek]

you can remove lines 4-6 on that file

Whoops! I thought I had removed them :-)

Updated in my latest push!

[akien-mga]

Thanks!