remove feature bolt 6.0

Author: MaxAake

packages/testkit-backend/src/feature/common.js

@@ -28,7 +28,6 @@ const features = [
   'Feature:Bolt:5.6',
   'Feature:Bolt:5.7',
   'Feature:Bolt:5.8',
-  'Feature:Bolt:6.0',
   'Feature:Bolt:HandshakeManifestV1',
   'Feature:Bolt:Patch:UTC',
   'Feature:API:ConnectionAcquisitionTimeout',