Upgrade to 6.3.4
Upgrade to 6.3.4

Changes in Docker image:

- Change version string in Dockerfile to 6.3.4.

Changes in Seafile Pro Edition: (source:
https://manual.seafile.com/changelog/changelog-for-seafile-professional-server.html)

- [fix] Fix a bug in creating group-owned library

xama5/docker-seafile-pro