[CI] Fix fetching in cmake configuration - #6303

Add explicit authentication using gh before call to setup-git and remove old username configuration

So to make sure this call to docker works for cloning project inside of a cmake call I tried a minimal example using a simple cmake project cloning a private repository with the docker image used by the CI. The current master version of the call (only calling gh auth setup-git) was sufficient on my end. So this means that the builder is correctly authenticated but github still refuses the access to public repository.

Here I am trying to add a new level of authentication to make sure the builder is logged-in. Let's see how it goes.

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