Give PrivateStorage Tahoe-LAFS 1.14

868bdea18361a0ca78ef8343018354232747de36 got rid of "tahoe-lafs"

19dd3895d4e7bd5d6205c0eebaba1c843c871e37 added "tahoe-lafs-1_14" and
"tahoe-lafs-master".

8c7a61c658e32eaccf666e5fe818a996c36a988f explicitly uses 1_14 for privatestorage.

nixpkgs.json

 { "name": "nixpkgs"
-, "url": "https://github.com/PrivateStorageio/nixpkgs/archive/e830c2bfd25926d2479f5cfb88a656a6dd9ce93a.tar.gz"
-, "sha256": "1jjslnl1v83317arafsp31jch00d4h98jv0ky0xvl7qblzb7ncvr"
+, "url": "https://github.com/PrivateStorageio/nixpkgs/archive/8c7a61c658e32eaccf666e5fe818a996c36a988f.tar.gz"
+, "sha256": "1ln0a8c20qykm57wl901lixny1fcfmzgbavd7pbjk6jbnfij59bl"
 }