Wrong app name in the app field pf a document metatag

[oleua]

Hi! The meta tags contain wrong information about the app the document was created. Should be euro-office.

[Mumrah213]

I've believe I tracked this down — the APPLICATION_NAME env var is set to onlyoffice in the standalone supervisor configs, which is in turn read by the x2t converter in the core repo. I'll open a PR - even if I am wrong I have a hard time seeing anything break from changing those from onlyoffice -> euro-office