Use repository name when uploading Docker image

[ranisalt]

Pull Request Prelude

• [x] I have followed proper The Forgotten Server code styling.
• [x] I have read and understood the contribution guidelines before making this PR.
• [x] I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

Uses repository owner/name when tagging and uploading the Docker image, that way on forks the action will work as is since it will upload to the owner's packages rather than trying to upload to @otland's packages (which would always fail on a fork)