Update references from master branch to main

[vojtechsokol]

Focus was on making the CI and GitHub actions work after the default
branch was switched from master to main.

See: OAMG-4907

[github-actions]

Thank you for contributing to the Leapp project!

Please note that every PR needs to comply with the Leapp Guidelines and must pass all tests in order to be mergeable.
If you want to request a review or rebuild a package in copr, you can use following commands as a comment:

• review please @oamg/developers to notify leapp developers of the review request
• /packit copr-build to submit a public copr build using packit

To launch regression testing public members of oamg organization can leave the following comment:

• /rerun to schedule basic regression tests using this pr build and leapp-repository*master* as artifacts
• /rerun 42 to schedule basic regression tests using this pr build and leapp-repository*PR42* as artifacts
• /rerun-sst to schedule sst tests using this pr build and leapp-repository*master* as artifacts
• /rerun-sst 42 to schedule sst tests using this pr build and leapp-repository*PR42* as artifacts

Please open ticket in case you experience technical problem with the CI. (RH internal only)

Note: In case there are problems with tests not being triggered automatically on new PR/commit or pending for a long time, please consider rerunning the CI by commenting leapp-ci build (might require several comments). If the problem persists, contact leapp-infra.

[matejmatuska]

LGTM. The actions have ran and Makefile works correctly. The commit message could mention it's about GH actions or CI though.

[matejmatuska]

Merged, there were 2 timeouted tests, but that's unrelated to these changes