IONOS(richdocuments): update submodule (gate creation for public shares)

6b8957bfc..593107e1a:
  593107e1a IONOS: fix: do not offer document creation to public share visitors

Restores the ionos-dev-v30 behaviour that anonymous public share visitors
are not offered Collabora document creation. The v30 patch worked through
the legacy OCA.Files.NewFileMenu plugin, which no longer exists in the
NC33 line, so the gate now lives in RegisterTemplateFileCreatorListener.

Ported from ionos-dev-v30 richdocuments:
  f1db58f79 IONOS: fix: for shares allow document creation only for users
            that can edit

Author: printminion-co