Remove feature flag drop_license_management_artifact completly

Why are we doing this work

We have a feature flag drop_license_management_artifact that is enabled by default, the feature works so we can remove this flag completely

Relevant links

1. Feature flag file https://gitlab.com/gitlab-org/gitlab/-/blob/ddad0826d4c87ace97288a4d5bcbd91c2f42443d/config/feature_flags/development/drop_license_management_artifact.yml

Implementation plan

• remove code related to parsing license_management report.
• remove license_management artifact type.
• remove feature flag from the codebase
• remove feature flag from GitLab.com