distributed fs: remove sheepdog (unmaintained since 2018)

- https://github.com/sheepdog/sheepdog/commits/master
- ref. https://github.com/awesome-foss/awesome-sysadmin/issues/405

README.md

@@ -326,7 +326,6 @@ _See also: [awesome-selfhosted/Database Management](https://github.com/awesome-s
 - [MooseFS](https://moosefs.com/) - Fault tolerant, network distributed file system. ([Source Code](https://github.com/moosefs/moosefs))
 - [OpenAFS](https://www.openafs.org/) - Distributed network file system with read-only replicas and multi-OS support. ([Source Code](https://git.openafs.org/?p=openafs.git;a=summary))
 - [Perkeep](https://perkeep.org/) - A set of open source formats, protocols, and software for modeling, storing, searching, sharing and synchronizing data (previously Camlistore). ([Source Code](https://github.com/perkeep/perkeep))
-- [SheepDog](https://sheepdog.github.io/sheepdog/) - A distributed Blockdevice, Rest, QEMU and distributed Filesystem storage. ([Source Code](https://github.com/sheepdog/sheepdog))
 - [Openstack Swift](https://docs.openstack.org/developer/swift/) - A highly available, distributed, eventually consistent object/blob store. ([Source Code](https://opendev.org/openstack/swift))
 - [TahoeLAFS](https://tahoe-lafs.org/trac/tahoe-lafs) - secure, decentralized, fault-tolerant, peer-to-peer distributed data store and distributed file system. ([Source Code](https://github.com/tahoe-lafs/tahoe-lafs))
 - [XtreemFS](https://www.xtreemfs.org/) - XtreemFS is a fault-tolerant distributed file system for all storage needs. ([Source Code](https://github.com/xtreemfs/xtreemfs))