Update the Release workflows

[jtpio]

Similar to jupyterlab/jupyterlab-github#154, we should update the releaser workflows to be able to make releases from the repo, without having to use a bot account.

See jupyter-server/jupyter_releaser#557 for more context.

cc @Zsailer

[jtpio]

The GitHub app seems to already be installed on the repo:

[davidbrochart]

Done in #267.