Enable mobile web view for OnlyOffice

[mmattel]

References: owncloud/ocis#11661 (feat: [issues/OCISDEV-305] Enable the mobile web view for OnlyOffice)

[mmattel]

Mentioned in: owncloud/docs-main#128 (Add ocis 7.3 release notes)
Fixed in: #1196 (Prepare changes for 7.3 (Balch) )