Enhancement: Update reva to v1.6.1-0.20210326165326-e8a00d9b2368

* quota querying and tree accounting [cs3org/reva#1405](https://github.com/cs3org/reva/pull/1405)
* Fix webdav file versions endpoint bugs [cs3org/reva#1526](https://github.com/cs3org/reva/pull/1526)
* Fix etag changing only once a second [cs3org/reva#1576](https://github.com/cs3org/reva/pull/1576)
* Trashbin API parity [cs3org/reva#1552](https://github.com/cs3org/reva/pull/1552)
* Signature authentication for public links [cs3org/reva#1590](https://github.com/cs3org/reva/pull/1590)

https://github.com/owncloud/ocis/pull/1683
https://github.com/cs3org/reva/pull/1405
https://github.com/owncloud/ocis/pull/1861
