Manually returning a license is usually never necessary, unless when running into an unrecoverable error while having a license active.
Also, Unity only allows returning professional licenses.
You may use Unity - Return license to return your license and free up a spot towards the maximum number of active licenses.
Add this step to your workflow:
# Return License
- name: Return license
uses: game-ci/unity-return-license@v1
if: always()