Update background of favicon-fb.png
Update background of favicon-fb.png

Signed-off-by: wernerfred <5b8ef92852e8089df746d17c429ffc99fe641b79@fim.uni-passau.de>

nextcloud/server,nextcloud/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,nextcloud/server,andreas-p/nextcloud-server,nextcloud/server