Use `git config 'http.https://github.com/.extraheader'` instead of external `github-token` param

[MingweiSamuel]

Repos checked out by actions/checkout have an authentication header included which can be used to push changes back to the repository, no need for the user to manually generate and specify a github-token param.

[MingweiSamuel]

The token may still be needed for commenting

[ktrz]

Hi @MingweiSamuel As specified in the docs the github-token is necessary for adding commit comments https://github.com/benchmark-action/github-action-benchmark#commit-comment

It is also necessary in case of scheduled and manual runs to fetch the commit data as it's not included in the payload data with those events