[ upstream commit 802d25447fa1d325d3713220f8ad08e7938f6dd4 ]

Commit 50df544 added a new job in the end-to-end workflows to checkout
the tested code and run paths-filter on it. That first job fails when
the workflows are scheduled (vs. triggered by PR comment) because we try
to grab the pull request URL, which doesn't exist:

    curl ${{ github.event.issue.pull_request.url }} > pr.json

results in error:

    Run curl  > pr.json
    curl: try 'curl --help' or 'curl --manual' for more information

We can avoid this by skipping steps in the first job when triggered by
schedule. We can't skip the entire first job because the second job has
a dependency on the first and would fail if we skipped the first.

Fixes: 50df544 (".github: Skip unnecessary ci-xxx tests")
Signed-off-by: Paul Chaignon <paul@cilium.io>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>