doc: Update license file and contributing guide

PR Checklist

[x] Added label to the Pull Request for easier discoverability and search
[x] Commit Message meets guidelines as indicated in the URL https://github.com/intel-retail/retail-use-cases/blob/main/CONTRIBUTING.md
[x] Every commit is a single defect fix and does not mix feature addition or changes
[ ] Unit Tests have been added for new changes
[x] Updated Documentation as relevant to the changes
[ ] All commented code has been removed
[ ] If you've added a dependency, you've ensured license is compatible with repository license and clearly outlined the added dependency.
[ ] PR change contains code related to security
[ ] PR introduces changes that breaks compatibility with other modules (If YES, please provide details below)

Small update for license

close: #issue_number