Bugfix: Update reva to v2.19.8

We updated reva to v2.19.8

*   Fix [cs3org/reva#4761](https://github.com/cs3org/reva/pull/4761): Quotes in dav Content-Disposition header
*   Fix [cs3org/reva#4853](https://github.com/cs3org/reva/pull/4853): Write upload session info atomically
*   Enh [cs3org/reva#4701](https://github.com/cs3org/reva/pull/4701): Extend service account permissions

https://github.com/owncloud/ocis/pull/10138
https://github.com/owncloud/ocis/pull/10103
