Unhelpful flathub finish-args-unnecessary-xdg-config-access error

[Stephan Bergmann]

A recent org.libreoffice.LibreOffice PR test build at 
<https://buildbot.flathub.org/#/builders/6/builds/89263> suddenly 
started to fail in a "Validate manifest" step with

> flatpak run --command=flatpak-builder-lint org.flatpak.Builder --exceptions manifest org.libreoffice.LibreOffice.json
>  in dir /srv/buildbot/worker/build-aarch64-7/build (timeout 1200 secs)
>  watching logfiles {}
>  argv: b'flatpak run --command=flatpak-builder-lint org.flatpak.Builder --exceptions manifest org.libreoffice.LibreOffice.json'
>  using PTY: False
> {
>     "errors": [
>         "finish-args-unnecessary-xdg-config-access"
>     ]
> }
> program finished with exit code 1
> elapsedTime=0.907696

Now, my guess would be that it wants to complain about any of the three 
lines at 
<https://github.com/flathub/org.libreoffice.LibreOffice/blob/bf0eb94c248865432fbdb9283b2407f179afe9f9/org.libreoffice.LibreOffice.json#L828>,

>         "--filesystem=xdg-config/gtk-3.0",

(once added with 
<https://github.com/flathub/org.libreoffice.LibreOffice/commit/e2376fbfdb12b9fca44c9413d08f2ed35b7b3d2f> 
" Adding access to gtk-3.0 config, mainly to give access to bookmarks 
for the file picker")

>         "--filesystem=xdg-config/fontconfig:ro",

(once added with 
<https://github.com/flathub/org.libreoffice.LibreOffice/commit/c80b412af7ec1d15b49c64ec6590450e9bacd3f2> 
" fix missing user-installed fonts")

>         "--filesystem=xdg-run/gvfsd",

(once added with 
<https://github.com/flathub/org.libreoffice.LibreOffice/commit/4226084c374eac66c520837a81c517a98541543d> 
"Adding xdg-run/gvfsd").

But which of those three lines (if any) are supposed to be problematic, 
and why?