New upstream release: 6.0.0

[jacobzimmermann]

Please confirm your submission meets all the criteria

• [x] I have read the App Requirements and App Maintenance pages.
• [x] My pull request follows the instructions at App Submission.
• [x] I am using only the minimal set of permissions. (If not, please explain each non-standard permission.)
• [x] All assets referenced in the manifest are redistributable by any party. If not, the unredistributable parts are using an extra-data source type.
• [x] I am an upstream contributor to the project. If not, I contacted upstream developers about submitting their software to Flathub. Link:
• [ ] I own the domain used in the application ID or the domain has a policy for delegating subdomains (e.g. GitHub, SourceForge).
• [x] Any additional patches or files have been submitted to the upstream projects concerned. (If not, explain why.)

[flathubbot]

Started test build 49568

[flathubbot]

Started test build 49569

[flathubbot]

Build 49568 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/32170/org.omegat.OmegaT.flatpakref