util/HashRing: remove obsolete class

Consistent Hashing was obsoleted by Rendezvous Hashing.

Author: MaxKellermann

src/util/HashRing.hxx

@@ -4,7 +4,6 @@ test(
     'TestUtil',
     'TestCRC32.cxx',
     'TestException.cxx',
-    'TestHashRing.cxx',
     'TestHexParse.cxx',
     'TestIntrusiveForwardList.cxx',
     'TestIntrusiveHashSet.cxx',